From aefd0e1f7dc75dbeff340e04471cf8edae94cf01 Mon Sep 17 00:00:00 2001
From: Yonas Habteab <yonas.habteab@netways.de>
Date: Wed, 22 Sep 2021 10:21:15 +0200
Subject: [PATCH] Add PHP 7 argument & return type declarations to all member
 methods

---
 application/controllers/CommentController.php |  2 +-
 application/controllers/ConfigController.php  |  2 +-
 .../controllers/DowntimeController.php        |  2 +-
 application/controllers/HostController.php    |  9 +--
 application/controllers/HostsController.php   |  3 +-
 application/controllers/ServiceController.php |  6 +-
 .../controllers/ServicesController.php        |  5 +-
 application/forms/Command/CommandForm.php     |  2 +-
 .../Instance/ToggleInstanceFeaturesForm.php   |  6 +-
 .../Command/Object/AcknowledgeProblemForm.php |  3 +
 .../forms/Command/Object/AddCommentForm.php   |  3 +
 .../forms/Command/Object/CheckNowForm.php     |  3 +
 .../Command/Object/DeleteCommentForm.php      |  3 +
 .../Command/Object/DeleteDowntimeForm.php     |  3 +
 .../Command/Object/ProcessCheckResultForm.php |  3 +
 .../Object/RemoveAcknowledgementForm.php      |  3 +
 .../Command/Object/ScheduleCheckForm.php      |  3 +
 .../Object/ScheduleHostDowntimeForm.php       |  3 +
 .../Object/ScheduleServiceDowntimeForm.php    |  3 +
 .../Object/SendCustomNotificationForm.php     |  3 +
 .../Object/ToggleObjectFeaturesForm.php       |  2 +-
 application/forms/Navigation/ActionForm.php   |  3 -
 application/forms/RedisConfigForm.php         |  6 +-
 .../Authentication/ObjectAuthorization.php    |  8 +--
 library/Icingadb/Command/IcingaApiCommand.php | 26 ++++++--
 library/Icingadb/Command/IcingaCommand.php    |  2 +-
 .../Instance/ToggleInstanceFeatureCommand.php | 16 +++--
 .../Object/AcknowledgeProblemCommand.php      | 24 +++----
 .../Command/Object/AddCommentCommand.php      |  6 +-
 .../Icingadb/Command/Object/CommandAuthor.php | 12 +++-
 .../Command/Object/DeleteCommentCommand.php   | 10 ++-
 .../Command/Object/DeleteDowntimeCommand.php  | 10 ++-
 .../Command/Object/GetObjectCommand.php       |  8 +--
 .../Icingadb/Command/Object/ObjectCommand.php | 10 ++-
 .../Object/ProcessCheckResultCommand.php      | 24 ++++---
 .../Object/PropagateHostDowntimeCommand.php   |  6 +-
 .../Command/Object/ScheduleCheckCommand.php   | 18 ++++--
 .../Object/ScheduleHostDowntimeCommand.php    |  6 +-
 .../Object/ScheduleServiceDowntimeCommand.php | 40 ++++++++----
 .../Object/SendCustomNotificationCommand.php  |  4 +-
 .../Object/ToggleObjectFeatureCommand.php     | 18 ++++--
 .../Command/Object/WithCommentCommand.php     | 12 +++-
 .../Renderer/IcingaApiCommandRenderer.php     | 32 +++++-----
 .../Command/Transport/ApiCommandTransport.php | 53 +++++++++++----
 .../Command/Transport/CommandTransport.php    |  8 ++-
 .../Transport/CommandTransportInterface.php   |  2 +-
 library/Icingadb/Common/Auth.php              | 15 +++--
 library/Icingadb/Common/BaseFilter.php        |  6 +-
 library/Icingadb/Common/BaseItemList.php      |  4 +-
 library/Icingadb/Common/BaseListItem.php      | 16 +++--
 .../Icingadb/Common/BaseOrderedListItem.php   | 10 ++-
 library/Icingadb/Common/BaseStatusBar.php     |  4 +-
 library/Icingadb/Common/BaseTableRowItem.php  |  9 ++-
 library/Icingadb/Common/CaptionDisabled.php   |  4 +-
 library/Icingadb/Common/CommandActions.php    |  8 ++-
 library/Icingadb/Common/Database.php          |  2 +-
 library/Icingadb/Common/DetailActions.php     | 14 ++--
 library/Icingadb/Common/HostLink.php          |  3 +-
 library/Icingadb/Common/HostLinks.php         | 26 ++++----
 library/Icingadb/Common/HostStates.php        |  6 +-
 library/Icingadb/Common/IcingaRedis.php       | 29 ++++++++-
 library/Icingadb/Common/Links.php             | 50 +++++++--------
 library/Icingadb/Common/LoadMore.php          |  8 +--
 library/Icingadb/Common/NoSubjectLink.php     |  4 +-
 .../Common/ObjectInspectionDetail.php         | 33 +++++++---
 .../Icingadb/Common/ObjectLinkDisabled.php    |  4 +-
 library/Icingadb/Common/ServiceLink.php       |  3 +-
 library/Icingadb/Common/ServiceLinks.php      | 24 +++----
 library/Icingadb/Common/ServiceStates.php     |  6 +-
 library/Icingadb/Common/StateBadges.php       | 30 ++++++---
 library/Icingadb/Common/ViewMode.php          |  4 +-
 library/Icingadb/Compat/CompatObject.php      | 15 +++--
 library/Icingadb/Compat/CompatService.php     |  2 +-
 library/Icingadb/Compat/UrlMigrator.php       | 55 ++++++++++------
 library/Icingadb/Data/PivotTable.php          | 44 ++++++++-----
 library/Icingadb/Hook/TabHook/HookActions.php |  6 +-
 library/Icingadb/Model/Behavior/ReRoute.php   |  2 +-
 library/Icingadb/Model/CustomvarFlat.php      |  2 +-
 library/Icingadb/Model/HostState.php          |  4 +-
 library/Icingadb/Model/ServiceState.php       |  4 +-
 .../Icingadb/ProvidedHook/IcingaHealth.php    |  6 +-
 library/Icingadb/ProvidedHook/RedisHealth.php |  2 +-
 library/Icingadb/ProvidedHook/X509/Sni.php    |  3 +-
 library/Icingadb/Redis/VolatileState.php      |  2 +-
 library/Icingadb/Setup/ApiTransportPage.php   |  2 +-
 library/Icingadb/Setup/DbResourcePage.php     |  2 +-
 library/Icingadb/Util/FeatureStatus.php       |  4 +-
 library/Icingadb/Util/PerfData.php            | 64 +++++++++----------
 library/Icingadb/Util/PerfDataFormat.php      | 26 ++++----
 library/Icingadb/Util/PerfDataSet.php         | 12 ++--
 library/Icingadb/Util/PluginOutput.php        |  2 +-
 library/Icingadb/Util/ThresholdRange.php      | 12 ++--
 .../Icingadb/Web/Control/ProblemToggle.php    |  4 +-
 .../Control/SearchBar/ObjectSuggestions.php   | 17 +++--
 .../Icingadb/Web/Control/ViewModeSwitcher.php | 12 ++--
 library/Icingadb/Web/Controller.php           | 27 ++++----
 library/Icingadb/Web/Navigation/Action.php    |  2 +-
 .../Navigation/Renderer/HostProblemsBadge.php |  3 +-
 .../Web/Navigation/Renderer/ProblemsBadge.php | 22 +++++--
 .../Renderer/ServiceProblemsBadge.php         |  3 +-
 library/Icingadb/Widget/AttemptBall.php       |  2 +-
 library/Icingadb/Widget/CheckAttempt.php      |  2 +-
 .../Icingadb/Widget/Detail/CommentDetail.php  |  7 +-
 .../Icingadb/Widget/Detail/DowntimeDetail.php |  4 +-
 library/Icingadb/Widget/Detail/HostDetail.php |  5 +-
 .../Icingadb/Widget/Detail/HostStatistics.php |  7 +-
 .../Widget/Detail/MultiselectQuickActions.php |  4 +-
 .../Icingadb/Widget/Detail/ObjectDetail.php   | 22 +++----
 .../Widget/Detail/ObjectStatistics.php        |  7 +-
 .../Icingadb/Widget/Detail/ObjectsDetail.php  | 25 ++++++--
 .../Icingadb/Widget/Detail/PerfDataTable.php  |  4 +-
 .../Icingadb/Widget/Detail/QuickActions.php   |  2 +-
 .../Widget/Detail/ServiceStatistics.php       |  7 +-
 library/Icingadb/Widget/Detail/UserDetail.php | 14 ++--
 .../Widget/Detail/UsergroupDetail.php         |  6 +-
 library/Icingadb/Widget/HostStateBadges.php   |  7 +-
 library/Icingadb/Widget/HostStatusBar.php     |  2 +-
 .../Widget/ItemList/BaseDowntimeListItem.php  |  2 +-
 .../Widget/ItemList/BaseHistoryListItem.php   |  2 +-
 .../Widget/ItemList/BaseHostListItem.php      |  6 ++
 .../ItemList/BaseNotificationListItem.php     |  2 +-
 .../Widget/ItemList/CommandTransportList.php  |  2 +-
 .../Icingadb/Widget/ItemList/CommentList.php  |  2 +-
 .../Icingadb/Widget/ItemList/DowntimeList.php |  2 +-
 .../Icingadb/Widget/ItemList/HistoryList.php  |  2 +-
 .../Widget/ItemList/HistoryListItem.php       |  2 +-
 .../ItemList/HistoryListItemDetailed.php      |  2 +-
 .../ItemList/HistoryListItemMinimal.php       |  2 +-
 .../Widget/ItemList/HostDetailHeader.php      |  2 +-
 library/Icingadb/Widget/ItemList/HostList.php |  2 +-
 .../Icingadb/Widget/ItemList/HostListItem.php |  2 +-
 .../Widget/ItemList/HostListItemDetailed.php  |  2 +-
 .../Widget/ItemList/HostListItemMinimal.php   |  2 +-
 .../Widget/ItemList/HostgroupList.php         |  2 +-
 .../Widget/ItemList/NotificationList.php      |  2 +-
 .../Widget/ItemList/NotificationListItem.php  |  2 +-
 .../ItemList/NotificationListItemDetailed.php |  2 +-
 .../ItemList/NotificationListItemMinimal.php  |  2 +-
 .../Widget/ItemList/PageSeparatorItem.php     |  2 +-
 .../Widget/ItemList/ServiceDetailHeader.php   |  2 +-
 .../Icingadb/Widget/ItemList/ServiceList.php  |  2 +-
 .../Widget/ItemList/ServiceListItem.php       |  2 +-
 .../ItemList/ServiceListItemDetailed.php      |  2 +-
 .../ItemList/ServiceListItemMinimal.php       |  2 +-
 .../Widget/ItemList/ServicegroupList.php      |  2 +-
 .../Widget/ItemList/StateListItem.php         |  2 +-
 library/Icingadb/Widget/ItemList/UserList.php |  2 +-
 .../Widget/ItemList/UsergroupList.php         |  2 +-
 library/Icingadb/Widget/MarkdownLine.php      |  2 +-
 library/Icingadb/Widget/MarkdownText.php      |  2 +-
 .../Icingadb/Widget/ServiceStateBadges.php    |  7 +-
 library/Icingadb/Widget/ServiceStatusBar.php  |  2 +-
 library/Icingadb/Widget/ShowMore.php          |  8 +--
 library/Icingadb/Widget/StateBadge.php        |  2 +-
 library/Icingadb/Widget/StateChange.php       |  2 +-
 library/Icingadb/Widget/TagList.php           |  4 +-
 156 files changed, 821 insertions(+), 520 deletions(-)

diff --git a/application/controllers/CommentController.php b/application/controllers/CommentController.php
index 7c49a4ed..16ae5c6c 100644
--- a/application/controllers/CommentController.php
+++ b/application/controllers/CommentController.php
@@ -61,7 +61,7 @@ class CommentController extends Controller
         $this->setAutorefreshInterval(10);
     }
 
-    protected function fetchCommandTargets()
+    protected function fetchCommandTargets(): array
     {
         return [$this->comment];
     }
diff --git a/application/controllers/ConfigController.php b/application/controllers/ConfigController.php
index 9b6069da..0d64fbfe 100644
--- a/application/controllers/ConfigController.php
+++ b/application/controllers/ConfigController.php
@@ -51,7 +51,7 @@ class ConfigController extends Controller
         $this->addContent(new HtmlString($form->render()));
     }
 
-    protected function mergeTabs(Tabs $tabs)
+    protected function mergeTabs(Tabs $tabs): self
     {
         /** @var Tab $tab */
         foreach ($tabs->getTabs() as $tab) {
diff --git a/application/controllers/DowntimeController.php b/application/controllers/DowntimeController.php
index e6fc2607..c9b69cf2 100644
--- a/application/controllers/DowntimeController.php
+++ b/application/controllers/DowntimeController.php
@@ -72,7 +72,7 @@ class DowntimeController extends Controller
         $this->setAutorefreshInterval(10);
     }
 
-    protected function fetchCommandTargets()
+    protected function fetchCommandTargets(): array
     {
         return [$this->downtime];
     }
diff --git a/application/controllers/HostController.php b/application/controllers/HostController.php
index e3eedc16..535a98b6 100644
--- a/application/controllers/HostController.php
+++ b/application/controllers/HostController.php
@@ -25,6 +25,7 @@ use Icinga\Module\Icingadb\Widget\ItemList\HostList;
 use Icinga\Module\Icingadb\Widget\ItemList\HistoryList;
 use Icinga\Module\Icingadb\Widget\ItemList\ServiceList;
 use ipl\Web\Url;
+use ipl\Web\Widget\Tabs;
 
 class HostController extends Controller
 {
@@ -230,7 +231,7 @@ class HostController extends Controller
         $this->setAutorefreshInterval(10);
     }
 
-    protected function createTabs()
+    protected function createTabs(): Tabs
     {
         $tabs = $this->getTabs()
             ->add('index', [
@@ -260,7 +261,7 @@ class HostController extends Controller
         return $tabs;
     }
 
-    protected function setTitleTab($name)
+    protected function setTitleTab(string $name)
     {
         $tab = $this->createTabs()->get($name);
 
@@ -271,7 +272,7 @@ class HostController extends Controller
         }
     }
 
-    protected function fetchCommandTargets()
+    protected function fetchCommandTargets(): array
     {
         return [$this->host];
     }
@@ -281,7 +282,7 @@ class HostController extends Controller
         return Links::host($this->host);
     }
 
-    protected function getDefaultTabControls()
+    protected function getDefaultTabControls(): array
     {
         return [(new HostList([$this->host]))->setDetailActionsDisabled()->setNoSubjectLink()];
     }
diff --git a/application/controllers/HostsController.php b/application/controllers/HostsController.php
index 512d33cc..a7fdd6ca 100644
--- a/application/controllers/HostsController.php
+++ b/application/controllers/HostsController.php
@@ -19,6 +19,7 @@ use Icinga\Module\Icingadb\Widget\ItemList\HostList;
 use Icinga\Module\Icingadb\Widget\HostStatusBar;
 use Icinga\Module\Icingadb\Widget\ShowMore;
 use Icinga\Module\Icingadb\Web\Control\ViewModeSwitcher;
+use ipl\Orm\Query;
 use ipl\Stdlib\Filter;
 use ipl\Web\Control\LimitControl;
 use ipl\Web\Control\SortControl;
@@ -192,7 +193,7 @@ class HostsController extends Controller
         $this->setTitle(t('Adjust Filter'));
     }
 
-    protected function fetchCommandTargets()
+    protected function fetchCommandTargets(): Query
     {
         $db = $this->getDb();
 
diff --git a/application/controllers/ServiceController.php b/application/controllers/ServiceController.php
index be6de10b..e681bf48 100644
--- a/application/controllers/ServiceController.php
+++ b/application/controllers/ServiceController.php
@@ -206,7 +206,7 @@ class ServiceController extends Controller
         return $tabs;
     }
 
-    protected function setTitleTab($name)
+    protected function setTitleTab(string $name)
     {
         $tab = $this->createTabs()->get($name);
 
@@ -217,7 +217,7 @@ class ServiceController extends Controller
         }
     }
 
-    protected function fetchCommandTargets()
+    protected function fetchCommandTargets(): array
     {
         return [$this->service];
     }
@@ -227,7 +227,7 @@ class ServiceController extends Controller
         return Links::service($this->service, $this->service->host);
     }
 
-    protected function getDefaultTabControls()
+    protected function getDefaultTabControls(): array
     {
         return [(new ServiceList([$this->service]))->setDetailActionsDisabled()->setNoSubjectLink()];
     }
diff --git a/application/controllers/ServicesController.php b/application/controllers/ServicesController.php
index cd0bda7b..228c6c76 100644
--- a/application/controllers/ServicesController.php
+++ b/application/controllers/ServicesController.php
@@ -22,6 +22,7 @@ use Icinga\Module\Icingadb\Widget\ServiceStatusBar;
 use Icinga\Module\Icingadb\Widget\ShowMore;
 use Icinga\Module\Icingadb\Web\Control\ViewModeSwitcher;
 use ipl\Html\HtmlString;
+use ipl\Orm\Query;
 use ipl\Stdlib\Filter;
 use ipl\Web\Control\LimitControl;
 use ipl\Web\Control\SortControl;
@@ -314,7 +315,7 @@ class ServicesController extends Controller
         $this->setAutorefreshInterval(30);
     }
 
-    protected function fetchCommandTargets()
+    protected function fetchCommandTargets(): Query
     {
         $db = $this->getDb();
 
@@ -351,7 +352,7 @@ class ServicesController extends Controller
         return new FeatureStatus('service', $summary->first());
     }
 
-    public function createProblemToggle()
+    public function createProblemToggle(): ProblemToggle
     {
         $filter = $this->params->shift('problems');
 
diff --git a/application/forms/Command/CommandForm.php b/application/forms/Command/CommandForm.php
index 4169493b..7fb79663 100644
--- a/application/forms/Command/CommandForm.php
+++ b/application/forms/Command/CommandForm.php
@@ -39,7 +39,7 @@ abstract class CommandForm extends Form
      *
      * @return $this
      */
-    public function setObjects($objects)
+    public function setObjects($objects): self
     {
         $this->objects = $objects;
 
diff --git a/application/forms/Command/Instance/ToggleInstanceFeaturesForm.php b/application/forms/Command/Instance/ToggleInstanceFeaturesForm.php
index 55c9b5b0..eb270dab 100644
--- a/application/forms/Command/Instance/ToggleInstanceFeaturesForm.php
+++ b/application/forms/Command/Instance/ToggleInstanceFeaturesForm.php
@@ -26,7 +26,7 @@ class ToggleInstanceFeaturesForm extends CommandForm
      */
     protected $submittedFeatures = [];
 
-    public function __construct($featureStatus)
+    public function __construct(array $featureStatus)
     {
         $this->featureStatus = $featureStatus;
         $this->features = [
@@ -136,7 +136,7 @@ class ToggleInstanceFeaturesForm extends CommandForm
     {
     }
 
-    protected function getCommand(Model $object)
+    protected function getCommand(Model $object): \Generator
     {
         foreach ($this->features as $feature => $spec) {
             $featureState = $this->getElement($feature)->isChecked();
@@ -147,7 +147,7 @@ class ToggleInstanceFeaturesForm extends CommandForm
 
             $command = new ToggleInstanceFeatureCommand();
             $command->setFeature($feature);
-            $command->setEnabled((int) $featureState);
+            $command->setEnabled($featureState);
 
             $this->submittedFeatures[] = $command;
 
diff --git a/application/forms/Command/Object/AcknowledgeProblemForm.php b/application/forms/Command/Object/AcknowledgeProblemForm.php
index c5b9e21a..5ca70740 100644
--- a/application/forms/Command/Object/AcknowledgeProblemForm.php
+++ b/application/forms/Command/Object/AcknowledgeProblemForm.php
@@ -176,6 +176,9 @@ class AcknowledgeProblemForm extends CommandForm
         (new IcingaFormDecorator())->decorate($this->getElement('btn_submit'));
     }
 
+    /**
+     * @return ?AcknowledgeProblemCommand
+     */
     protected function getCommand(Model $object)
     {
         if (! $this->isGrantedOn('icingadb/command/acknowledge-problem', $object)) {
diff --git a/application/forms/Command/Object/AddCommentForm.php b/application/forms/Command/Object/AddCommentForm.php
index 3d910342..af75f86e 100644
--- a/application/forms/Command/Object/AddCommentForm.php
+++ b/application/forms/Command/Object/AddCommentForm.php
@@ -130,6 +130,9 @@ class AddCommentForm extends CommandForm
         (new IcingaFormDecorator())->decorate($this->getElement('btn_submit'));
     }
 
+    /**
+     * @return ?AddCommentCommand
+     */
     protected function getCommand(Model $object)
     {
         if (! $this->isGrantedOn('icingadb/command/comment/add', $object)) {
diff --git a/application/forms/Command/Object/CheckNowForm.php b/application/forms/Command/Object/CheckNowForm.php
index dbd76b1b..136b40ea 100644
--- a/application/forms/Command/Object/CheckNowForm.php
+++ b/application/forms/Command/Object/CheckNowForm.php
@@ -46,6 +46,9 @@ class CheckNowForm extends CommandForm
         );
     }
 
+    /**
+     * @return ?ScheduleCheckCommand
+     */
     protected function getCommand(Model $object)
     {
         if (
diff --git a/application/forms/Command/Object/DeleteCommentForm.php b/application/forms/Command/Object/DeleteCommentForm.php
index 0abc9582..e4630a24 100644
--- a/application/forms/Command/Object/DeleteCommentForm.php
+++ b/application/forms/Command/Object/DeleteCommentForm.php
@@ -53,6 +53,9 @@ class DeleteCommentForm extends CommandForm
         );
     }
 
+    /**
+     * @return ?DeleteCommentCommand
+     */
     protected function getCommand(Model $object)
     {
         if (! $this->isGrantedOn('icingadb/command/comment/delete', $object->{$object->object_type})) {
diff --git a/application/forms/Command/Object/DeleteDowntimeForm.php b/application/forms/Command/Object/DeleteDowntimeForm.php
index 72c4d22f..c34c9a89 100644
--- a/application/forms/Command/Object/DeleteDowntimeForm.php
+++ b/application/forms/Command/Object/DeleteDowntimeForm.php
@@ -67,6 +67,9 @@ class DeleteDowntimeForm extends CommandForm
         );
     }
 
+    /**
+     * @return ?DeleteDowntimeCommand
+     */
     protected function getCommand(Model $object)
     {
         if (
diff --git a/application/forms/Command/Object/ProcessCheckResultForm.php b/application/forms/Command/Object/ProcessCheckResultForm.php
index d9d6608d..e7e23e79 100644
--- a/application/forms/Command/Object/ProcessCheckResultForm.php
+++ b/application/forms/Command/Object/ProcessCheckResultForm.php
@@ -136,6 +136,9 @@ class ProcessCheckResultForm extends CommandForm
         (new IcingaFormDecorator())->decorate($this->getElement('btn_submit'));
     }
 
+    /**
+     * @return ?ProcessCheckResultCommand
+     */
     protected function getCommand(Model $object)
     {
         if (
diff --git a/application/forms/Command/Object/RemoveAcknowledgementForm.php b/application/forms/Command/Object/RemoveAcknowledgementForm.php
index 16488b4c..a69706a7 100644
--- a/application/forms/Command/Object/RemoveAcknowledgementForm.php
+++ b/application/forms/Command/Object/RemoveAcknowledgementForm.php
@@ -63,6 +63,9 @@ class RemoveAcknowledgementForm extends CommandForm
         );
     }
 
+    /**
+     * @return ?RemoveAcknowledgementCommand
+     */
     protected function getCommand(Model $object)
     {
         if (! $this->isGrantedOn('icingadb/command/remove-acknowledgement', $object)) {
diff --git a/application/forms/Command/Object/ScheduleCheckForm.php b/application/forms/Command/Object/ScheduleCheckForm.php
index 4354ef9a..853516f2 100644
--- a/application/forms/Command/Object/ScheduleCheckForm.php
+++ b/application/forms/Command/Object/ScheduleCheckForm.php
@@ -109,6 +109,9 @@ class ScheduleCheckForm extends CommandForm
         (new IcingaFormDecorator())->decorate($this->getElement('btn_submit'));
     }
 
+    /**
+     * @return ?ScheduleCheckCommand
+     */
     protected function getCommand(Model $object)
     {
         if (
diff --git a/application/forms/Command/Object/ScheduleHostDowntimeForm.php b/application/forms/Command/Object/ScheduleHostDowntimeForm.php
index 7ab1176f..081316b8 100644
--- a/application/forms/Command/Object/ScheduleHostDowntimeForm.php
+++ b/application/forms/Command/Object/ScheduleHostDowntimeForm.php
@@ -87,6 +87,9 @@ class ScheduleHostDowntimeForm extends ScheduleServiceDowntimeForm
         $decorator->decorate($this->getElement('child_options'));
     }
 
+    /**
+     * @return ?PropagateHostDowntimeCommand|ScheduleHostDowntimeCommand
+     */
     protected function getCommand(Model $object)
     {
         if (! $this->isGrantedOn('icingadb/command/downtime/schedule', $object)) {
diff --git a/application/forms/Command/Object/ScheduleServiceDowntimeForm.php b/application/forms/Command/Object/ScheduleServiceDowntimeForm.php
index 67e161bf..05453e24 100644
--- a/application/forms/Command/Object/ScheduleServiceDowntimeForm.php
+++ b/application/forms/Command/Object/ScheduleServiceDowntimeForm.php
@@ -227,6 +227,9 @@ class ScheduleServiceDowntimeForm extends CommandForm
         (new IcingaFormDecorator())->decorate($this->getElement('btn_submit'));
     }
 
+    /**
+     * @return ?ScheduleServiceDowntimeCommand
+     */
     protected function getCommand(Model $object)
     {
         if (! $this->isGrantedOn('icingadb/command/downtime/schedule', $object)) {
diff --git a/application/forms/Command/Object/SendCustomNotificationForm.php b/application/forms/Command/Object/SendCustomNotificationForm.php
index 052f80a3..9813def1 100644
--- a/application/forms/Command/Object/SendCustomNotificationForm.php
+++ b/application/forms/Command/Object/SendCustomNotificationForm.php
@@ -109,6 +109,9 @@ class SendCustomNotificationForm extends CommandForm
         (new IcingaFormDecorator())->decorate($this->getElement('btn_submit'));
     }
 
+    /**
+     * @return ?SendCustomNotificationCommand
+     */
     protected function getCommand(Model $object)
     {
         if (! $this->isGrantedOn('icingadb/command/send-custom-notification', $object)) {
diff --git a/application/forms/Command/Object/ToggleObjectFeaturesForm.php b/application/forms/Command/Object/ToggleObjectFeaturesForm.php
index e60234a3..faaeeaf4 100644
--- a/application/forms/Command/Object/ToggleObjectFeaturesForm.php
+++ b/application/forms/Command/Object/ToggleObjectFeaturesForm.php
@@ -148,7 +148,7 @@ class ToggleObjectFeaturesForm extends CommandForm
     {
     }
 
-    protected function getCommand(Model $object)
+    protected function getCommand(Model $object): \Generator
     {
         foreach ($this->features as $feature => $spec) {
             $featureState = $this->getElement($feature)->isChecked();
diff --git a/application/forms/Navigation/ActionForm.php b/application/forms/Navigation/ActionForm.php
index 86a6d082..08cba3f8 100644
--- a/application/forms/Navigation/ActionForm.php
+++ b/application/forms/Navigation/ActionForm.php
@@ -19,9 +19,6 @@ class ActionForm extends NavigationItemForm
      */
     protected $restriction;
 
-    /**
-     * {@inheritdoc}
-     */
     public function createElements(array $formData)
     {
         parent::createElements($formData);
diff --git a/application/forms/RedisConfigForm.php b/application/forms/RedisConfigForm.php
index 1786c03d..ec217956 100644
--- a/application/forms/RedisConfigForm.php
+++ b/application/forms/RedisConfigForm.php
@@ -194,7 +194,7 @@ class RedisConfigForm extends ConfigForm
         );
     }
 
-    public static function addSkipValidationCheckbox($form)
+    public static function addSkipValidationCheckbox(Form $form)
     {
         $form->addElement(
             'checkbox',
@@ -435,7 +435,7 @@ class RedisConfigForm extends ConfigForm
         return $this;
     }
 
-    public static function checkRedis(Form $form)
+    public static function checkRedis(Form $form): bool
     {
         $sections = [];
 
@@ -520,7 +520,7 @@ class RedisConfigForm extends ConfigForm
      *
      * @return  array               Callback validator
      */
-    private function wrapIplValidator($cls, $element, Closure $additionalValidator = null)
+    private function wrapIplValidator(string $cls, string $element, Closure $additionalValidator = null): array
     {
         return [
             'Callback',
diff --git a/library/Icingadb/Authentication/ObjectAuthorization.php b/library/Icingadb/Authentication/ObjectAuthorization.php
index e2b14cf5..5cbbd672 100644
--- a/library/Icingadb/Authentication/ObjectAuthorization.php
+++ b/library/Icingadb/Authentication/ObjectAuthorization.php
@@ -38,7 +38,7 @@ class ObjectAuthorization
      *
      * @return bool
      */
-    public static function grantsOn($permission, Model $for)
+    public static function grantsOn(string $permission, Model $for): bool
     {
         $self = new static();
 
@@ -72,7 +72,7 @@ class ObjectAuthorization
      *
      * @return bool
      */
-    public static function grantsOnType($permission, $type, Filter\Rule $filter, $cache = true)
+    public static function grantsOnType(string $permission, string $type, Filter\Rule $filter, bool $cache = true): bool
     {
         switch ($type) {
             case 'host':
@@ -142,7 +142,7 @@ class ObjectAuthorization
      *
      * @return void
      */
-    protected function loadGrants($model, Filter\Rule $filter, $cacheKey, $cache = true)
+    protected function loadGrants(string $model, Filter\Rule $filter, string $cacheKey, bool $cache = true)
     {
         /** @var Model $model */
         $query = $model::on($this->getDb());
@@ -234,7 +234,7 @@ class ObjectAuthorization
      *
      * @return bool
      */
-    protected function checkGrants($permission, $roles)
+    protected function checkGrants(string $permission, array $roles): bool
     {
         if (empty($roles)) {
             return false;
diff --git a/library/Icingadb/Command/IcingaApiCommand.php b/library/Icingadb/Command/IcingaApiCommand.php
index abfba29f..f3f0c335 100644
--- a/library/Icingadb/Command/IcingaApiCommand.php
+++ b/library/Icingadb/Command/IcingaApiCommand.php
@@ -35,7 +35,7 @@ class IcingaApiCommand
      *
      * @return  static
      */
-    public static function create($endpoint, array $data)
+    public static function create(string $endpoint, array $data): self
     {
         return (new static())
             ->setEndpoint($endpoint)
@@ -47,8 +47,14 @@ class IcingaApiCommand
      *
      * @return array
      */
-    public function getData()
+    public function getData(): array
     {
+        if ($this->data === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->data;
     }
 
@@ -59,7 +65,7 @@ class IcingaApiCommand
      *
      * @return  $this
      */
-    public function setData($data)
+    public function setData(array $data): self
     {
         $this->data = $data;
 
@@ -71,8 +77,14 @@ class IcingaApiCommand
      *
      * @return string
      */
-    public function getEndpoint()
+    public function getEndpoint(): string
     {
+        if ($this->endpoint === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->endpoint;
     }
 
@@ -83,7 +95,7 @@ class IcingaApiCommand
      *
      * @return  $this
      */
-    public function setEndpoint($endpoint)
+    public function setEndpoint(string $endpoint): self
     {
         $this->endpoint = $endpoint;
 
@@ -95,7 +107,7 @@ class IcingaApiCommand
      *
      * @return string
      */
-    public function getMethod()
+    public function getMethod(): string
     {
         return $this->method;
     }
@@ -107,7 +119,7 @@ class IcingaApiCommand
      *
      * @return $this
      */
-    public function setMethod($method)
+    public function setMethod(string $method): self
     {
         $this->method = $method;
 
diff --git a/library/Icingadb/Command/IcingaCommand.php b/library/Icingadb/Command/IcingaCommand.php
index 08a48729..7b5c5cff 100644
--- a/library/Icingadb/Command/IcingaCommand.php
+++ b/library/Icingadb/Command/IcingaCommand.php
@@ -14,7 +14,7 @@ abstract class IcingaCommand
      *
      * @return string
      */
-    public function getName()
+    public function getName(): string
     {
         $nsParts = explode('\\', get_called_class());
         return substr_replace(end($nsParts), '', -7);  // Remove 'Command' Suffix
diff --git a/library/Icingadb/Command/Instance/ToggleInstanceFeatureCommand.php b/library/Icingadb/Command/Instance/ToggleInstanceFeatureCommand.php
index 581f1c9f..d275d9b3 100644
--- a/library/Icingadb/Command/Instance/ToggleInstanceFeatureCommand.php
+++ b/library/Icingadb/Command/Instance/ToggleInstanceFeatureCommand.php
@@ -62,9 +62,9 @@ class ToggleInstanceFeatureCommand extends IcingaCommand
      *
      * @return  $this
      */
-    public function setFeature($feature)
+    public function setFeature(string $feature): self
     {
-        $this->feature = (string) $feature;
+        $this->feature = $feature;
 
         return $this;
     }
@@ -74,8 +74,12 @@ class ToggleInstanceFeatureCommand extends IcingaCommand
      *
      * @return string
      */
-    public function getFeature()
+    public function getFeature(): string
     {
+        if ($this->feature === null) {
+            throw new \LogicException('You have to set the feature first before getting it.');
+        }
+
         return $this->feature;
     }
 
@@ -86,9 +90,9 @@ class ToggleInstanceFeatureCommand extends IcingaCommand
      *
      * @return  $this
      */
-    public function setEnabled($enabled = true)
+    public function setEnabled(bool $enabled = true): self
     {
-        $this->enabled = (bool) $enabled;
+        $this->enabled = $enabled;
 
         return $this;
     }
@@ -96,7 +100,7 @@ class ToggleInstanceFeatureCommand extends IcingaCommand
     /**
      * Get whether the feature should be enabled or disabled
      *
-     * @return bool
+     * @return ?bool
      */
     public function getEnabled()
     {
diff --git a/library/Icingadb/Command/Object/AcknowledgeProblemCommand.php b/library/Icingadb/Command/Object/AcknowledgeProblemCommand.php
index aaff0394..baae24c7 100644
--- a/library/Icingadb/Command/Object/AcknowledgeProblemCommand.php
+++ b/library/Icingadb/Command/Object/AcknowledgeProblemCommand.php
@@ -49,9 +49,9 @@ class AcknowledgeProblemCommand extends WithCommentCommand
      *
      * @return  $this
      */
-    public function setSticky($sticky = true)
+    public function setSticky(bool $sticky = true): self
     {
-        $this->sticky = (bool) $sticky;
+        $this->sticky = $sticky;
 
         return $this;
     }
@@ -61,7 +61,7 @@ class AcknowledgeProblemCommand extends WithCommentCommand
      *
      * @return bool
      */
-    public function getSticky()
+    public function getSticky(): bool
     {
         return $this->sticky;
     }
@@ -73,9 +73,9 @@ class AcknowledgeProblemCommand extends WithCommentCommand
      *
      * @return  $this
      */
-    public function setNotify($notify = true)
+    public function setNotify(bool $notify = true): self
     {
-        $this->notify = (bool) $notify;
+        $this->notify = $notify;
 
         return $this;
     }
@@ -85,7 +85,7 @@ class AcknowledgeProblemCommand extends WithCommentCommand
      *
      * @return bool
      */
-    public function getNotify()
+    public function getNotify(): bool
     {
         return $this->notify;
     }
@@ -97,9 +97,9 @@ class AcknowledgeProblemCommand extends WithCommentCommand
      *
      * @return  $this
      */
-    public function setPersistent($persistent = true)
+    public function setPersistent(bool $persistent = true): self
     {
-        $this->persistent = (bool) $persistent;
+        $this->persistent = $persistent;
 
         return $this;
     }
@@ -109,7 +109,7 @@ class AcknowledgeProblemCommand extends WithCommentCommand
      *
      * @return bool
      */
-    public function getPersistent()
+    public function getPersistent(): bool
     {
         return $this->persistent;
     }
@@ -121,9 +121,9 @@ class AcknowledgeProblemCommand extends WithCommentCommand
      *
      * @return  $this
      */
-    public function setExpireTime($expireTime)
+    public function setExpireTime(int $expireTime): self
     {
-        $this->expireTime = (int) $expireTime;
+        $this->expireTime = $expireTime;
 
         return $this;
     }
@@ -131,7 +131,7 @@ class AcknowledgeProblemCommand extends WithCommentCommand
     /**
      * Get the time when the acknowledgement should expire
      *
-     * @return int
+     * @return ?int
      */
     public function getExpireTime()
     {
diff --git a/library/Icingadb/Command/Object/AddCommentCommand.php b/library/Icingadb/Command/Object/AddCommentCommand.php
index d8171337..c853b257 100644
--- a/library/Icingadb/Command/Object/AddCommentCommand.php
+++ b/library/Icingadb/Command/Object/AddCommentCommand.php
@@ -23,9 +23,9 @@ class AddCommentCommand extends WithCommentCommand
      *
      * @return  $this
      */
-    public function setExpireTime($expireTime)
+    public function setExpireTime(int $expireTime): self
     {
-        $this->expireTime = (int) $expireTime;
+        $this->expireTime = $expireTime;
 
         return $this;
     }
@@ -33,7 +33,7 @@ class AddCommentCommand extends WithCommentCommand
     /**
      * Get the time when the acknowledgement should expire
      *
-     * @return int
+     * @return ?int
      */
     public function getExpireTime()
     {
diff --git a/library/Icingadb/Command/Object/CommandAuthor.php b/library/Icingadb/Command/Object/CommandAuthor.php
index fc8596ec..f323b633 100644
--- a/library/Icingadb/Command/Object/CommandAuthor.php
+++ b/library/Icingadb/Command/Object/CommandAuthor.php
@@ -20,9 +20,9 @@ trait CommandAuthor
      *
      * @return  $this
      */
-    public function setAuthor($author)
+    public function setAuthor(string $author): self
     {
-        $this->author = (string) $author;
+        $this->author = $author;
 
         return $this;
     }
@@ -32,8 +32,14 @@ trait CommandAuthor
      *
      * @return string
      */
-    public function getAuthor()
+    public function getAuthor(): string
     {
+        if ($this->author === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->author;
     }
 }
diff --git a/library/Icingadb/Command/Object/DeleteCommentCommand.php b/library/Icingadb/Command/Object/DeleteCommentCommand.php
index c30802e3..8bfc2a37 100644
--- a/library/Icingadb/Command/Object/DeleteCommentCommand.php
+++ b/library/Icingadb/Command/Object/DeleteCommentCommand.php
@@ -25,8 +25,14 @@ class DeleteCommentCommand extends IcingaCommand
      *
      * @return string
      */
-    public function getCommentName()
+    public function getCommentName(): string
     {
+        if ($this->commentName === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->commentName;
     }
 
@@ -37,7 +43,7 @@ class DeleteCommentCommand extends IcingaCommand
      *
      * @return  $this
      */
-    public function setCommentName($commentName)
+    public function setCommentName(string $commentName): self
     {
         $this->commentName = $commentName;
 
diff --git a/library/Icingadb/Command/Object/DeleteDowntimeCommand.php b/library/Icingadb/Command/Object/DeleteDowntimeCommand.php
index 6cb1b8d3..a0867fa9 100644
--- a/library/Icingadb/Command/Object/DeleteDowntimeCommand.php
+++ b/library/Icingadb/Command/Object/DeleteDowntimeCommand.php
@@ -29,8 +29,14 @@ class DeleteDowntimeCommand extends IcingaCommand
      *
      * @return string
      */
-    public function getDowntimeName()
+    public function getDowntimeName(): string
     {
+        if ($this->downtimeName === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->downtimeName;
     }
 
@@ -43,7 +49,7 @@ class DeleteDowntimeCommand extends IcingaCommand
      *
      * @return  $this
      */
-    public function setDowntimeName($downtimeName)
+    public function setDowntimeName(string $downtimeName): self
     {
         $this->downtimeName = $downtimeName;
 
diff --git a/library/Icingadb/Command/Object/GetObjectCommand.php b/library/Icingadb/Command/Object/GetObjectCommand.php
index a9a2fe87..372a555b 100644
--- a/library/Icingadb/Command/Object/GetObjectCommand.php
+++ b/library/Icingadb/Command/Object/GetObjectCommand.php
@@ -18,7 +18,7 @@ class GetObjectCommand extends ObjectCommand
      *
      * @return string
      */
-    public function getObjectName()
+    public function getObjectName(): string
     {
         switch (true) {
             case $this->object instanceof Service:
@@ -33,7 +33,7 @@ class GetObjectCommand extends ObjectCommand
      *
      * @return string
      */
-    public function getObjectPluralType()
+    public function getObjectPluralType(): string
     {
         switch (true) {
             case $this->object instanceof Host:
@@ -48,7 +48,7 @@ class GetObjectCommand extends ObjectCommand
     /**
      * Get the attributes to query
      *
-     * @return array
+     * @return ?array
      */
     public function getAttributes()
     {
@@ -62,7 +62,7 @@ class GetObjectCommand extends ObjectCommand
      *
      * @return $this
      */
-    public function setAttributes(array $attributes)
+    public function setAttributes(array $attributes): self
     {
         $this->attributes = $attributes;
 
diff --git a/library/Icingadb/Command/Object/ObjectCommand.php b/library/Icingadb/Command/Object/ObjectCommand.php
index dd252480..7dae7997 100644
--- a/library/Icingadb/Command/Object/ObjectCommand.php
+++ b/library/Icingadb/Command/Object/ObjectCommand.php
@@ -26,7 +26,7 @@ abstract class ObjectCommand extends IcingaCommand
      *
      * @return  $this
      */
-    public function setObject(Model $object)
+    public function setObject(Model $object): self
     {
         $this->object = $object;
 
@@ -38,8 +38,14 @@ abstract class ObjectCommand extends IcingaCommand
      *
      * @return Model
      */
-    public function getObject()
+    public function getObject(): Model
     {
+        if ($this->object === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->object;
     }
 }
diff --git a/library/Icingadb/Command/Object/ProcessCheckResultCommand.php b/library/Icingadb/Command/Object/ProcessCheckResultCommand.php
index 532b77be..24eb5dd0 100644
--- a/library/Icingadb/Command/Object/ProcessCheckResultCommand.php
+++ b/library/Icingadb/Command/Object/ProcessCheckResultCommand.php
@@ -67,9 +67,9 @@ class ProcessCheckResultCommand extends ObjectCommand
      *
      * @return  $this
      */
-    public function setStatus($status)
+    public function setStatus(int $status): self
     {
-        $this->status = (int) $status;
+        $this->status = $status;
 
         return $this;
     }
@@ -79,8 +79,14 @@ class ProcessCheckResultCommand extends ObjectCommand
      *
      * @return int
      */
-    public function getStatus()
+    public function getStatus(): int
     {
+        if ($this->status === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->status;
     }
 
@@ -91,9 +97,9 @@ class ProcessCheckResultCommand extends ObjectCommand
      *
      * @return  $this
      */
-    public function setOutput($output)
+    public function setOutput(string $output): self
     {
-        $this->output = (string) $output;
+        $this->output = $output;
 
         return $this;
     }
@@ -101,7 +107,7 @@ class ProcessCheckResultCommand extends ObjectCommand
     /**
      * Get the text output of the host or service check result
      *
-     * @return string
+     * @return ?string
      */
     public function getOutput()
     {
@@ -115,9 +121,9 @@ class ProcessCheckResultCommand extends ObjectCommand
      *
      * @return  $this
      */
-    public function setPerformanceData($performanceData)
+    public function setPerformanceData(string $performanceData): self
     {
-        $this->performanceData = (string) $performanceData;
+        $this->performanceData = $performanceData;
 
         return $this;
     }
@@ -125,7 +131,7 @@ class ProcessCheckResultCommand extends ObjectCommand
     /**
      * Get the performance data of the host or service check result
      *
-     * @return string
+     * @return ?string
      */
     public function getPerformanceData()
     {
diff --git a/library/Icingadb/Command/Object/PropagateHostDowntimeCommand.php b/library/Icingadb/Command/Object/PropagateHostDowntimeCommand.php
index 0b009760..88964fba 100644
--- a/library/Icingadb/Command/Object/PropagateHostDowntimeCommand.php
+++ b/library/Icingadb/Command/Object/PropagateHostDowntimeCommand.php
@@ -23,9 +23,9 @@ class PropagateHostDowntimeCommand extends ScheduleHostDowntimeCommand
      *
      * @return  $this
      */
-    public function setTriggered($triggered = true)
+    public function setTriggered(bool $triggered = true): self
     {
-        $this->triggered = (bool) $triggered;
+        $this->triggered = $triggered;
 
         return $this;
     }
@@ -35,7 +35,7 @@ class PropagateHostDowntimeCommand extends ScheduleHostDowntimeCommand
      *
      * @return bool
      */
-    public function getTriggered()
+    public function getTriggered(): bool
     {
         return $this->triggered;
     }
diff --git a/library/Icingadb/Command/Object/ScheduleCheckCommand.php b/library/Icingadb/Command/Object/ScheduleCheckCommand.php
index fafc9683..c3f20973 100644
--- a/library/Icingadb/Command/Object/ScheduleCheckCommand.php
+++ b/library/Icingadb/Command/Object/ScheduleCheckCommand.php
@@ -37,9 +37,9 @@ class ScheduleCheckCommand extends ObjectCommand
      *
      * @return  $this
      */
-    public function setCheckTime($checkTime)
+    public function setCheckTime(int $checkTime): self
     {
-        $this->checkTime = (int) $checkTime;
+        $this->checkTime = $checkTime;
 
         return $this;
     }
@@ -49,8 +49,14 @@ class ScheduleCheckCommand extends ObjectCommand
      *
      * @return int Unix timestamp
      */
-    public function getCheckTime()
+    public function getCheckTime(): int
     {
+        if ($this->checkTime === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->checkTime;
     }
 
@@ -61,9 +67,9 @@ class ScheduleCheckCommand extends ObjectCommand
      *
      * @return  $this
      */
-    public function setForced($forced = true)
+    public function setForced(bool $forced = true): self
     {
-        $this->forced = (bool) $forced;
+        $this->forced = $forced;
 
         return $this;
     }
@@ -73,7 +79,7 @@ class ScheduleCheckCommand extends ObjectCommand
      *
      * @return bool
      */
-    public function getForced()
+    public function getForced(): bool
     {
         return $this->forced;
     }
diff --git a/library/Icingadb/Command/Object/ScheduleHostDowntimeCommand.php b/library/Icingadb/Command/Object/ScheduleHostDowntimeCommand.php
index d6aafa56..0e4d84fa 100644
--- a/library/Icingadb/Command/Object/ScheduleHostDowntimeCommand.php
+++ b/library/Icingadb/Command/Object/ScheduleHostDowntimeCommand.php
@@ -23,9 +23,9 @@ class ScheduleHostDowntimeCommand extends ScheduleServiceDowntimeCommand
      *
      * @return  $this
      */
-    public function setForAllServices($forAllServices = true)
+    public function setForAllServices(bool $forAllServices = true): self
     {
-        $this->forAllServices = (bool) $forAllServices;
+        $this->forAllServices = $forAllServices;
 
         return $this;
     }
@@ -35,7 +35,7 @@ class ScheduleHostDowntimeCommand extends ScheduleServiceDowntimeCommand
      *
      * @return bool
      */
-    public function getForAllServices()
+    public function getForAllServices(): bool
     {
         return $this->forAllServices;
     }
diff --git a/library/Icingadb/Command/Object/ScheduleServiceDowntimeCommand.php b/library/Icingadb/Command/Object/ScheduleServiceDowntimeCommand.php
index 51d0a655..3bad28ef 100644
--- a/library/Icingadb/Command/Object/ScheduleServiceDowntimeCommand.php
+++ b/library/Icingadb/Command/Object/ScheduleServiceDowntimeCommand.php
@@ -64,9 +64,9 @@ class ScheduleServiceDowntimeCommand extends AddCommentCommand
      *
      * @return  $this
      */
-    public function setStart($start)
+    public function setStart(int $start): self
     {
-        $this->start = (int) $start;
+        $this->start = $start;
 
         return $this;
     }
@@ -76,8 +76,14 @@ class ScheduleServiceDowntimeCommand extends AddCommentCommand
      *
      * @return int Unix timestamp
      */
-    public function getStart()
+    public function getStart(): int
     {
+        if ($this->start === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->start;
     }
 
@@ -88,9 +94,9 @@ class ScheduleServiceDowntimeCommand extends AddCommentCommand
      *
      * @return  $this
      */
-    public function setEnd($end)
+    public function setEnd(int $end): self
     {
-        $this->end = (int) $end;
+        $this->end = $end;
 
         return $this;
     }
@@ -100,8 +106,14 @@ class ScheduleServiceDowntimeCommand extends AddCommentCommand
      *
      * @return int Unix timestamp
      */
-    public function getEnd()
+    public function getEnd(): int
     {
+        if ($this->start === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->end;
     }
 
@@ -112,9 +124,9 @@ class ScheduleServiceDowntimeCommand extends AddCommentCommand
      *
      * @return  $this
      */
-    public function setFixed($fixed = true)
+    public function setFixed(bool $fixed = true): self
     {
-        $this->fixed = (bool) $fixed;
+        $this->fixed = $fixed;
 
         return $this;
     }
@@ -124,7 +136,7 @@ class ScheduleServiceDowntimeCommand extends AddCommentCommand
      *
      * @return boolean
      */
-    public function getFixed()
+    public function getFixed(): bool
     {
         return $this->fixed;
     }
@@ -136,9 +148,9 @@ class ScheduleServiceDowntimeCommand extends AddCommentCommand
      *
      * @return  $this
      */
-    public function setTriggerId($triggerId)
+    public function setTriggerId(int $triggerId): self
     {
-        $this->triggerId = (int) $triggerId;
+        $this->triggerId = $triggerId;
 
         return $this;
     }
@@ -160,9 +172,9 @@ class ScheduleServiceDowntimeCommand extends AddCommentCommand
      *
      * @return  $this
      */
-    public function setDuration($duration)
+    public function setDuration(int $duration): self
     {
-        $this->duration = (int) $duration;
+        $this->duration = $duration;
 
         return $this;
     }
@@ -177,7 +189,7 @@ class ScheduleServiceDowntimeCommand extends AddCommentCommand
         return $this->duration;
     }
 
-    public function getName()
+    public function getName(): string
     {
         return 'ScheduleDowntime';
     }
diff --git a/library/Icingadb/Command/Object/SendCustomNotificationCommand.php b/library/Icingadb/Command/Object/SendCustomNotificationCommand.php
index af225939..de90620f 100644
--- a/library/Icingadb/Command/Object/SendCustomNotificationCommand.php
+++ b/library/Icingadb/Command/Object/SendCustomNotificationCommand.php
@@ -21,7 +21,7 @@ class SendCustomNotificationCommand extends WithCommentCommand
     /**
      * Get whether to force the notification
      *
-     * @return bool
+     * @return ?bool
      */
     public function getForced()
     {
@@ -35,7 +35,7 @@ class SendCustomNotificationCommand extends WithCommentCommand
      *
      * @return  $this
      */
-    public function setForced($forced = true)
+    public function setForced(bool $forced = true): self
     {
         $this->forced = $forced;
 
diff --git a/library/Icingadb/Command/Object/ToggleObjectFeatureCommand.php b/library/Icingadb/Command/Object/ToggleObjectFeatureCommand.php
index e54dbdb5..699a1133 100644
--- a/library/Icingadb/Command/Object/ToggleObjectFeatureCommand.php
+++ b/library/Icingadb/Command/Object/ToggleObjectFeatureCommand.php
@@ -59,9 +59,9 @@ class ToggleObjectFeatureCommand extends ObjectCommand
      *
      * @return  $this
      */
-    public function setFeature($feature)
+    public function setFeature(string $feature): self
     {
-        $this->feature = (string) $feature;
+        $this->feature = $feature;
 
         return $this;
     }
@@ -71,8 +71,14 @@ class ToggleObjectFeatureCommand extends ObjectCommand
      *
      * @return string
      */
-    public function getFeature()
+    public function getFeature(): string
     {
+        if ($this->feature === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->feature;
     }
 
@@ -83,9 +89,9 @@ class ToggleObjectFeatureCommand extends ObjectCommand
      *
      * @return  $this
      */
-    public function setEnabled($enabled = true)
+    public function setEnabled(bool $enabled = true): self
     {
-        $this->enabled = (bool) $enabled;
+        $this->enabled = $enabled;
 
         return $this;
     }
@@ -93,7 +99,7 @@ class ToggleObjectFeatureCommand extends ObjectCommand
     /**
      * Get whether the feature should be enabled or disabled
      *
-     * @return bool
+     * @return ?bool
      */
     public function getEnabled()
     {
diff --git a/library/Icingadb/Command/Object/WithCommentCommand.php b/library/Icingadb/Command/Object/WithCommentCommand.php
index fbc4a0dc..299c998f 100644
--- a/library/Icingadb/Command/Object/WithCommentCommand.php
+++ b/library/Icingadb/Command/Object/WithCommentCommand.php
@@ -25,9 +25,9 @@ abstract class WithCommentCommand extends ObjectCommand
      *
      * @return  $this
      */
-    public function setComment($comment)
+    public function setComment(string $comment): self
     {
-        $this->comment = (string) $comment;
+        $this->comment = $comment;
 
         return $this;
     }
@@ -37,8 +37,14 @@ abstract class WithCommentCommand extends ObjectCommand
      *
      * @return string
      */
-    public function getComment()
+    public function getComment(): string
     {
+        if ($this->comment === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->comment;
     }
 }
diff --git a/library/Icingadb/Command/Renderer/IcingaApiCommandRenderer.php b/library/Icingadb/Command/Renderer/IcingaApiCommandRenderer.php
index eedbf639..aa1cdbee 100644
--- a/library/Icingadb/Command/Renderer/IcingaApiCommandRenderer.php
+++ b/library/Icingadb/Command/Renderer/IcingaApiCommandRenderer.php
@@ -42,7 +42,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
      *
      * @return string
      */
-    public function getApp()
+    public function getApp(): string
     {
         return $this->app;
     }
@@ -54,7 +54,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
      *
      * @return  $this
      */
-    public function setApp($app)
+    public function setApp(string $app): self
     {
         $this->app = $app;
 
@@ -67,7 +67,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
      * @param   array   $data
      * @param   Model   $object
      *
-     * @return  array
+     * @return  void
      */
     protected function applyFilter(array &$data, Model $object)
     {
@@ -86,7 +86,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
      *
      * @return  IcingaApiCommand
      */
-    public function render(IcingaCommand $command)
+    public function render(IcingaCommand $command): IcingaApiCommand
     {
         $renderMethod = 'render' . $command->getName();
         if (! method_exists($this, $renderMethod)) {
@@ -98,7 +98,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
         return $this->$renderMethod($command);
     }
 
-    public function renderGetObject(GetObjectCommand $command)
+    public function renderGetObject(GetObjectCommand $command): IcingaApiCommand
     {
         $endpoint = sprintf(
             'objects/%s/%s',
@@ -114,7 +114,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
         return IcingaApiCommand::create($endpoint, $data)->setMethod('GET');
     }
 
-    public function renderAddComment(AddCommentCommand $command)
+    public function renderAddComment(AddCommentCommand $command): IcingaApiCommand
     {
         $endpoint = 'actions/add-comment';
         $data = [
@@ -130,7 +130,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
         return IcingaApiCommand::create($endpoint, $data);
     }
 
-    public function renderSendCustomNotification(SendCustomNotificationCommand $command)
+    public function renderSendCustomNotification(SendCustomNotificationCommand $command): IcingaApiCommand
     {
         $endpoint = 'actions/send-custom-notification';
         $data = [
@@ -143,7 +143,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
         return IcingaApiCommand::create($endpoint, $data);
     }
 
-    public function renderProcessCheckResult(ProcessCheckResultCommand $command)
+    public function renderProcessCheckResult(ProcessCheckResultCommand $command): IcingaApiCommand
     {
         $endpoint = 'actions/process-check-result';
         $data = [
@@ -156,7 +156,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
         return IcingaApiCommand::create($endpoint, $data);
     }
 
-    public function renderScheduleCheck(ScheduleCheckCommand $command)
+    public function renderScheduleCheck(ScheduleCheckCommand $command): IcingaApiCommand
     {
         $endpoint = 'actions/reschedule-check';
         $data = [
@@ -168,7 +168,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
         return IcingaApiCommand::create($endpoint, $data);
     }
 
-    public function renderScheduleDowntime(ScheduleServiceDowntimeCommand $command)
+    public function renderScheduleDowntime(ScheduleServiceDowntimeCommand $command): IcingaApiCommand
     {
         $endpoint = 'actions/schedule-downtime';
         $data = [
@@ -193,7 +193,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
         return IcingaApiCommand::create($endpoint, $data);
     }
 
-    public function renderAcknowledgeProblem(AcknowledgeProblemCommand $command)
+    public function renderAcknowledgeProblem(AcknowledgeProblemCommand $command): IcingaApiCommand
     {
         $endpoint = 'actions/acknowledge-problem';
         $data = [
@@ -212,7 +212,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
         return IcingaApiCommand::create($endpoint, $data);
     }
 
-    public function renderToggleObjectFeature(ToggleObjectFeatureCommand $command)
+    public function renderToggleObjectFeature(ToggleObjectFeatureCommand $command): IcingaApiCommand
     {
         switch ($command->getFeature()) {
             case ToggleObjectFeatureCommand::FEATURE_ACTIVE_CHECKS:
@@ -253,7 +253,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
         return IcingaApiCommand::create($endpoint, $data);
     }
 
-    public function renderDeleteComment(DeleteCommentCommand $command)
+    public function renderDeleteComment(DeleteCommentCommand $command): IcingaApiCommand
     {
         $endpoint = 'actions/remove-comment';
         $data = [
@@ -264,7 +264,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
         return IcingaApiCommand::create($endpoint, $data);
     }
 
-    public function renderDeleteDowntime(DeleteDowntimeCommand $command)
+    public function renderDeleteDowntime(DeleteDowntimeCommand $command): IcingaApiCommand
     {
         $endpoint = 'actions/remove-downtime';
         $data = [
@@ -275,7 +275,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
         return IcingaApiCommand::create($endpoint, $data);
     }
 
-    public function renderRemoveAcknowledgement(RemoveAcknowledgementCommand $command)
+    public function renderRemoveAcknowledgement(RemoveAcknowledgementCommand $command): IcingaApiCommand
     {
         $endpoint = 'actions/remove-acknowledgement';
         $data = ['author' => $command->getAuthor()];
@@ -284,7 +284,7 @@ class IcingaApiCommandRenderer implements IcingaCommandRendererInterface
         return IcingaApiCommand::create($endpoint, $data);
     }
 
-    public function renderToggleInstanceFeature(ToggleInstanceFeatureCommand $command)
+    public function renderToggleInstanceFeature(ToggleInstanceFeatureCommand $command): IcingaApiCommand
     {
         $endpoint = 'objects/icingaapplications/' . $this->getApp();
 
diff --git a/library/Icingadb/Command/Transport/ApiCommandTransport.php b/library/Icingadb/Command/Transport/ApiCommandTransport.php
index 52123a46..7838ad7b 100644
--- a/library/Icingadb/Command/Transport/ApiCommandTransport.php
+++ b/library/Icingadb/Command/Transport/ApiCommandTransport.php
@@ -74,7 +74,7 @@ class ApiCommandTransport implements CommandTransportInterface
      *
      * @return  $this
      */
-    public function setApp($app)
+    public function setApp(string $app): self
     {
         $this->renderer->setApp($app);
 
@@ -86,8 +86,14 @@ class ApiCommandTransport implements CommandTransportInterface
      *
      * @return string
      */
-    public function getHost()
+    public function getHost(): string
     {
+        if ($this->host === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->host;
     }
 
@@ -98,7 +104,7 @@ class ApiCommandTransport implements CommandTransportInterface
      *
      * @return  $this
      */
-    public function setHost($host)
+    public function setHost(string $host): self
     {
         $this->host = $host;
 
@@ -110,8 +116,14 @@ class ApiCommandTransport implements CommandTransportInterface
      *
      * @return string
      */
-    public function getPassword()
+    public function getPassword(): string
     {
+        if ($this->password === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->password;
     }
 
@@ -122,7 +134,7 @@ class ApiCommandTransport implements CommandTransportInterface
      *
      * @return  $this
      */
-    public function setPassword($password)
+    public function setPassword(string $password): self
     {
         $this->password = $password;
 
@@ -134,7 +146,7 @@ class ApiCommandTransport implements CommandTransportInterface
      *
      * @return int
      */
-    public function getPort()
+    public function getPort(): int
     {
         return $this->port;
     }
@@ -146,9 +158,9 @@ class ApiCommandTransport implements CommandTransportInterface
      *
      * @return  $this
      */
-    public function setPort($port)
+    public function setPort(int $port): self
     {
-        $this->port = (int) $port;
+        $this->port = $port;
 
         return $this;
     }
@@ -158,8 +170,14 @@ class ApiCommandTransport implements CommandTransportInterface
      *
      * @return string
      */
-    public function getUsername()
+    public function getUsername(): string
     {
+        if ($this->username === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->username;
     }
 
@@ -170,7 +188,7 @@ class ApiCommandTransport implements CommandTransportInterface
      *
      * @return  $this
      */
-    public function setUsername($username)
+    public function setUsername(string $username): self
     {
         $this->username = $username;
 
@@ -184,11 +202,18 @@ class ApiCommandTransport implements CommandTransportInterface
      *
      * @return  string
      */
-    protected function getUriFor($endpoint)
+    protected function getUriFor(string $endpoint): string
     {
         return sprintf('https://%s:%u/v1/%s', $this->getHost(), $this->getPort(), $endpoint);
     }
 
+    /**
+     * Send the given command to the icinga2's REST API
+     *
+     * @param IcingaApiCommand $command
+     *
+     * @return mixed
+     */
     protected function sendCommand(IcingaApiCommand $command)
     {
         Logger::debug(
@@ -268,8 +293,10 @@ class ApiCommandTransport implements CommandTransportInterface
      * @param   int|null        $now
      *
      * @throws  CommandTransportException
+     *
+     * @return  void
      */
-    public function send(IcingaCommand $command, $now = null)
+    public function send(IcingaCommand $command, int $now = null)
     {
         return $this->sendCommand($this->renderer->render($command));
     }
@@ -277,6 +304,8 @@ class ApiCommandTransport implements CommandTransportInterface
     /**
      * Try to connect to the API
      *
+     * @return void
+     *
      * @throws  CommandTransportException In case the connection was not successful
      */
     public function probe()
diff --git a/library/Icingadb/Command/Transport/CommandTransport.php b/library/Icingadb/Command/Transport/CommandTransport.php
index b9cd1470..9b2e9860 100644
--- a/library/Icingadb/Command/Transport/CommandTransport.php
+++ b/library/Icingadb/Command/Transport/CommandTransport.php
@@ -30,7 +30,7 @@ class CommandTransport implements CommandTransportInterface
      *
      * @throws  ConfigurationError
      */
-    public static function getConfig()
+    public static function getConfig(): Config
     {
         if (static::$config === null) {
             $config = Config::module('icingadb', 'commandtransports');
@@ -56,7 +56,7 @@ class CommandTransport implements CommandTransportInterface
      *
      * @throws  ConfigurationError
      */
-    public static function createTransport(ConfigObject $config)
+    public static function createTransport(ConfigObject $config): ApiCommandTransport
     {
         $config = clone $config;
         switch (strtolower($config->transport)) {
@@ -97,8 +97,10 @@ class CommandTransport implements CommandTransportInterface
      * @param   int|null        $now        Timestamp of the command or null for now
      *
      * @throws  CommandTransportException   If sending the Icinga command failed
+     *
+     * @return  void
      */
-    public function send(IcingaCommand $command, $now = null)
+    public function send(IcingaCommand $command, int $now = null)
     {
         $errors = [];
 
diff --git a/library/Icingadb/Command/Transport/CommandTransportInterface.php b/library/Icingadb/Command/Transport/CommandTransportInterface.php
index 567275ae..ad07cb90 100644
--- a/library/Icingadb/Command/Transport/CommandTransportInterface.php
+++ b/library/Icingadb/Command/Transport/CommandTransportInterface.php
@@ -19,5 +19,5 @@ interface CommandTransportInterface
      *
      * @throws  CommandTransportException If sending the Icinga command failed
      */
-    public function send(IcingaCommand $command, $now = null);
+    public function send(IcingaCommand $command, int $now = null);
 }
diff --git a/library/Icingadb/Common/Auth.php b/library/Icingadb/Common/Auth.php
index 1ffcde64..e61a962b 100644
--- a/library/Icingadb/Common/Auth.php
+++ b/library/Icingadb/Common/Auth.php
@@ -4,6 +4,7 @@
 
 namespace Icinga\Module\Icingadb\Common;
 
+use Icinga\Authentication\Auth as IcingaAuth;
 use Icinga\Exception\ConfigurationError;
 use Icinga\Module\Icingadb\Authentication\ObjectAuthorization;
 use Icinga\Util\StringHelper;
@@ -17,9 +18,9 @@ use ipl\Web\Filter\QueryString;
 
 trait Auth
 {
-    public function getAuth()
+    public function getAuth(): IcingaAuth
     {
-        return \Icinga\Authentication\Auth::getInstance();
+        return IcingaAuth::getInstance();
     }
 
     /**
@@ -29,7 +30,7 @@ trait Auth
      *
      * @return bool
      */
-    public function isPermittedRoute($name)
+    public function isPermittedRoute(string $name): bool
     {
         if ($this->getAuth()->getUser()->isUnrestricted()) {
             return true;
@@ -51,7 +52,7 @@ trait Auth
      *
      * @return bool
      */
-    public function isGrantedOn($permission, Model $object)
+    public function isGrantedOn(string $permission, Model $object): bool
     {
         if ($this->getAuth()->getUser()->isUnrestricted()) {
             return $this->getAuth()->hasPermission($permission);
@@ -76,7 +77,7 @@ trait Auth
      *
      * @return bool
      */
-    public function isGrantedOnType($permission, $type, Filter\Rule $filter, $cache = true)
+    public function isGrantedOnType(string $permission, string $type, Filter\Rule $filter, bool $cache = true): bool
     {
         if ($this->getAuth()->getUser()->isUnrestricted()) {
             return $this->getAuth()->hasPermission($permission);
@@ -247,7 +248,7 @@ trait Auth
      *
      * @return Filter\Rule
      */
-    protected function parseRestriction($queryString, $restriction)
+    protected function parseRestriction(string $queryString, string $restriction): Filter\Rule
     {
         $allowedColumns = [
             'host.name',
@@ -311,7 +312,7 @@ trait Auth
      *
      * @return Filter\None
      */
-    protected function parseBlacklist($blacklist, $column)
+    protected function parseBlacklist(string $blacklist, string $column): Filter\None
     {
         $filter = Filter::none();
         foreach (explode(',', $blacklist) as $value) {
diff --git a/library/Icingadb/Common/BaseFilter.php b/library/Icingadb/Common/BaseFilter.php
index b1080d2a..a4f69837 100644
--- a/library/Icingadb/Common/BaseFilter.php
+++ b/library/Icingadb/Common/BaseFilter.php
@@ -16,7 +16,7 @@ trait BaseFilter
      *
      * @return bool
      */
-    public function hasBaseFilter()
+    public function hasBaseFilter(): bool
     {
         return $this->baseFilter !== null;
     }
@@ -24,7 +24,7 @@ trait BaseFilter
     /**
      * Get the base filter
      *
-     * @return Rule
+     * @return ?Rule
      */
     public function getBaseFilter()
     {
@@ -38,7 +38,7 @@ trait BaseFilter
      *
      * @return $this
      */
-    public function setBaseFilter(Rule $baseFilter = null)
+    public function setBaseFilter(Rule $baseFilter = null): self
     {
         $this->baseFilter = $baseFilter;
 
diff --git a/library/Icingadb/Common/BaseItemList.php b/library/Icingadb/Common/BaseItemList.php
index 5e29dcbe..7eacb28e 100644
--- a/library/Icingadb/Common/BaseItemList.php
+++ b/library/Icingadb/Common/BaseItemList.php
@@ -49,14 +49,14 @@ abstract class BaseItemList extends BaseHtmlElement
         $this->init();
     }
 
-    abstract protected function getItemClass();
+    abstract protected function getItemClass(): string;
 
     /**
      * Get whether the list contains at least one item with an icon_image
      *
      * @return bool
      */
-    public function hasIconImages()
+    public function hasIconImages(): bool
     {
         return $this->hasIconImages;
     }
diff --git a/library/Icingadb/Common/BaseListItem.php b/library/Icingadb/Common/BaseListItem.php
index 02eb4900..c552bb64 100644
--- a/library/Icingadb/Common/BaseListItem.php
+++ b/library/Icingadb/Common/BaseListItem.php
@@ -66,7 +66,7 @@ abstract class BaseListItem extends BaseHtmlElement
     {
     }
 
-    protected function createCaption()
+    protected function createCaption(): BaseHtmlElement
     {
         $caption = Html::tag('section', ['class' => 'caption']);
 
@@ -75,7 +75,7 @@ abstract class BaseListItem extends BaseHtmlElement
         return $caption;
     }
 
-    protected function createHeader()
+    protected function createHeader(): BaseHtmlElement
     {
         $header = Html::tag('header');
 
@@ -84,7 +84,7 @@ abstract class BaseListItem extends BaseHtmlElement
         return $header;
     }
 
-    protected function createMain()
+    protected function createMain(): BaseHtmlElement
     {
         $main = Html::tag('div', ['class' => 'main']);
 
@@ -93,7 +93,7 @@ abstract class BaseListItem extends BaseHtmlElement
         return $main;
     }
 
-    protected function createFooter()
+    protected function createFooter(): BaseHtmlElement
     {
         $footer = new HtmlElement('footer');
 
@@ -102,6 +102,9 @@ abstract class BaseListItem extends BaseHtmlElement
         return $footer;
     }
 
+    /**
+     * @return ?BaseHtmlElement
+     */
     protected function createIconImage()
     {
         if (! $this->list->hasIconImages()) {
@@ -121,7 +124,7 @@ abstract class BaseListItem extends BaseHtmlElement
     {
     }
 
-    protected function createTitle()
+    protected function createTitle(): BaseHtmlElement
     {
         $title = HTML::tag('div', ['class' => 'title']);
 
@@ -130,6 +133,9 @@ abstract class BaseListItem extends BaseHtmlElement
         return $title;
     }
 
+    /**
+     * @return ?BaseHtmlElement
+     */
     protected function createVisual()
     {
         $visual = Html::tag('div', ['class' => 'visual']);
diff --git a/library/Icingadb/Common/BaseOrderedListItem.php b/library/Icingadb/Common/BaseOrderedListItem.php
index 22357901..bf0f2b2a 100644
--- a/library/Icingadb/Common/BaseOrderedListItem.php
+++ b/library/Icingadb/Common/BaseOrderedListItem.php
@@ -16,9 +16,9 @@ abstract class BaseOrderedListItem extends BaseListItem
      *
      * @return $this
      */
-    public function setOrder($order)
+    public function setOrder(int $order): self
     {
-        $this->order = (int) $order;
+        $this->order = $order;
 
         return $this;
     }
@@ -30,6 +30,12 @@ abstract class BaseOrderedListItem extends BaseListItem
      */
     public function getOrder()
     {
+        if ($this->order === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->order;
     }
 }
diff --git a/library/Icingadb/Common/BaseStatusBar.php b/library/Icingadb/Common/BaseStatusBar.php
index 9f3b23b7..7339eb20 100644
--- a/library/Icingadb/Common/BaseStatusBar.php
+++ b/library/Icingadb/Common/BaseStatusBar.php
@@ -24,9 +24,9 @@ abstract class BaseStatusBar extends BaseHtmlElement
 
     abstract protected function assembleTotal(BaseHtmlElement $total);
 
-    abstract protected function createStateBadges();
+    abstract protected function createStateBadges(): BaseHtmlElement;
 
-    protected function createCount()
+    protected function createCount(): BaseHtmlElement
     {
         $total = Html::tag('span', ['class' => 'item-count']);
 
diff --git a/library/Icingadb/Common/BaseTableRowItem.php b/library/Icingadb/Common/BaseTableRowItem.php
index 642cf290..d3e00366 100644
--- a/library/Icingadb/Common/BaseTableRowItem.php
+++ b/library/Icingadb/Common/BaseTableRowItem.php
@@ -47,12 +47,12 @@ abstract class BaseTableRowItem extends BaseHtmlElement
     {
     }
 
-    protected function createColumn($content = null)
+    protected function createColumn($content = null): BaseHtmlElement
     {
         return Html::tag('div', ['class' => 'col'], $content);
     }
 
-    protected function createColumns()
+    protected function createColumns(): HtmlDocument
     {
         $columns = new HtmlDocument();
 
@@ -61,7 +61,7 @@ abstract class BaseTableRowItem extends BaseHtmlElement
         return $columns;
     }
 
-    protected function createTitle()
+    protected function createTitle(): BaseHtmlElement
     {
         $title = $this->createColumn()->addAttributes(['class' => 'title']);
 
@@ -70,6 +70,9 @@ abstract class BaseTableRowItem extends BaseHtmlElement
         return $title;
     }
 
+    /**
+     * @return ?BaseHtmlElement
+     */
     protected function createVisual()
     {
         $visual = new HtmlElement('div', Attributes::create(['class' => 'visual']));
diff --git a/library/Icingadb/Common/CaptionDisabled.php b/library/Icingadb/Common/CaptionDisabled.php
index 7f5c8adc..26344c51 100644
--- a/library/Icingadb/Common/CaptionDisabled.php
+++ b/library/Icingadb/Common/CaptionDisabled.php
@@ -11,7 +11,7 @@ trait CaptionDisabled
     /**
      * @return bool
      */
-    public function isCaptionDisabled()
+    public function isCaptionDisabled(): bool
     {
         return $this->captionDisabled;
     }
@@ -21,7 +21,7 @@ trait CaptionDisabled
      *
      * @return $this
      */
-    public function setCaptionDisabled($captionDisabled = true)
+    public function setCaptionDisabled(bool $captionDisabled = true): self
     {
         $this->captionDisabled = $captionDisabled;
 
diff --git a/library/Icingadb/Common/CommandActions.php b/library/Icingadb/Common/CommandActions.php
index 2086db97..3283964b 100644
--- a/library/Icingadb/Common/CommandActions.php
+++ b/library/Icingadb/Common/CommandActions.php
@@ -74,7 +74,7 @@ trait CommandActions
      *
      * @return Model
      */
-    protected function getCommandTargetModel()
+    protected function getCommandTargetModel(): Model
     {
         if (! isset($this->commandTargetModel)) {
             $commandTargets = $this->getCommandTargets();
@@ -95,7 +95,7 @@ trait CommandActions
      *
      * @return bool
      */
-    protected function isGrantedOnCommandTargets($permission)
+    protected function isGrantedOnCommandTargets(string $permission): bool
     {
         $commandTargets = $this->getCommandTargets();
         if (is_array($commandTargets)) {
@@ -122,7 +122,7 @@ trait CommandActions
      *
      * @throws SecurityException
      */
-    protected function assertIsGrantedOnCommandTargets($permission)
+    protected function assertIsGrantedOnCommandTargets(string $permission)
     {
         if (! $this->isGrantedOnCommandTargets($permission)) {
             throw new SecurityException('No permission for %s', $permission);
@@ -133,6 +133,8 @@ trait CommandActions
      * Handle and register the given command form
      *
      * @param string|CommandForm $form
+     *
+     * @return void
      */
     protected function handleCommandForm($form)
     {
diff --git a/library/Icingadb/Common/Database.php b/library/Icingadb/Common/Database.php
index d4c7479d..f7097ba7 100644
--- a/library/Icingadb/Common/Database.php
+++ b/library/Icingadb/Common/Database.php
@@ -23,7 +23,7 @@ trait Database
      *
      * @throws ConfigurationError If the related resource configuration does not exist
      */
-    public function getDb()
+    public function getDb(): Connection
     {
         if ($this->db === null) {
             $config = new SqlConfig(ResourceFactory::getResourceConfig(
diff --git a/library/Icingadb/Common/DetailActions.php b/library/Icingadb/Common/DetailActions.php
index 6e1b4a03..e92c80d6 100644
--- a/library/Icingadb/Common/DetailActions.php
+++ b/library/Icingadb/Common/DetailActions.php
@@ -21,7 +21,7 @@ trait DetailActions
      *
      * @return $this
      */
-    public function setDetailActionsDisabled($state = true)
+    public function setDetailActionsDisabled(bool $state = true): self
     {
         $this->detailActionsDisabled = $state;
 
@@ -33,7 +33,7 @@ trait DetailActions
      *
      * @return bool
      */
-    public function getDetailActionsDisabled()
+    public function getDetailActionsDisabled(): bool
     {
         return $this->detailActionsDisabled;
     }
@@ -43,7 +43,7 @@ trait DetailActions
      *
      * @return $this
      */
-    public function initializeDetailActions()
+    public function initializeDetailActions(): self
     {
         $this->getAttributes()
             ->registerAttributeCallback('class', function () {
@@ -63,7 +63,7 @@ trait DetailActions
      *
      * @return $this
      */
-    protected function setMultiselectUrl(Url $url)
+    protected function setMultiselectUrl(Url $url): self
     {
         /** @var BaseHtmlElement $this */
         $this->getAttributes()
@@ -81,7 +81,7 @@ trait DetailActions
      *
      * @return $this
      */
-    protected function setDetailUrl(Url $url)
+    protected function setDetailUrl(Url $url): self
     {
         /** @var BaseHtmlElement $this */
         $this->getAttributes()
@@ -100,7 +100,7 @@ trait DetailActions
      *
      * @return $this
      */
-    public function addMultiselectFilterAttribute(BaseHtmlElement $element, Filter\Rule $filter)
+    public function addMultiselectFilterAttribute(BaseHtmlElement $element, Filter\Rule $filter): self
     {
         $element->getAttributes()
             ->registerAttributeCallback('data-icinga-multiselect-filter', function () use ($filter) {
@@ -118,7 +118,7 @@ trait DetailActions
      *
      * @return $this
      */
-    public function addDetailFilterAttribute(BaseHtmlElement $element, Filter\Rule $filter)
+    public function addDetailFilterAttribute(BaseHtmlElement $element, Filter\Rule $filter): self
     {
         $element->getAttributes()
             ->registerAttributeCallback('data-icinga-detail-filter', function () use ($filter) {
diff --git a/library/Icingadb/Common/HostLink.php b/library/Icingadb/Common/HostLink.php
index 081c485e..51386bf5 100644
--- a/library/Icingadb/Common/HostLink.php
+++ b/library/Icingadb/Common/HostLink.php
@@ -5,12 +5,13 @@
 namespace Icinga\Module\Icingadb\Common;
 
 use Icinga\Module\Icingadb\Model\Host;
+use ipl\Html\BaseHtmlElement;
 use ipl\Html\Html;
 use ipl\Web\Widget\StateBall;
 
 trait HostLink
 {
-    protected function createHostLink(Host $host, $withStateBall = false)
+    protected function createHostLink(Host $host, bool $withStateBall = false): BaseHtmlElement
     {
         $content = [];
 
diff --git a/library/Icingadb/Common/HostLinks.php b/library/Icingadb/Common/HostLinks.php
index 1a044606..e8f28800 100644
--- a/library/Icingadb/Common/HostLinks.php
+++ b/library/Icingadb/Common/HostLinks.php
@@ -9,67 +9,67 @@ use ipl\Web\Url;
 
 abstract class HostLinks
 {
-    public static function acknowledge(Host $host)
+    public static function acknowledge(Host $host): Url
     {
         return Url::fromPath('icingadb/host/acknowledge', ['name' => $host->name]);
     }
 
-    public static function addComment(Host $host)
+    public static function addComment(Host $host): Url
     {
         return Url::fromPath('icingadb/host/add-comment', ['name' => $host->name]);
     }
 
-    public static function checkNow(Host $host)
+    public static function checkNow(Host $host): Url
     {
         return Url::fromPath('icingadb/host/check-now', ['name' => $host->name]);
     }
 
-    public static function scheduleCheck(Host $host)
+    public static function scheduleCheck(Host $host): Url
     {
         return Url::fromPath('icingadb/host/schedule-check', ['name' => $host->name]);
     }
 
-    public static function comments(Host $host)
+    public static function comments(Host $host): Url
     {
         return Url::fromPath('icingadb/comments', ['host.name' => $host->name]);
     }
 
-    public static function downtimes(Host $host)
+    public static function downtimes(Host $host): Url
     {
         return Url::fromPath('icingadb/downtimes', ['host.name' => $host->name]);
     }
 
-    public static function history(Host $host)
+    public static function history(Host $host): Url
     {
         return Url::fromPath('icingadb/host/history', ['name' => $host->name]);
     }
 
-    public static function removeAcknowledgement(Host $host)
+    public static function removeAcknowledgement(Host $host): Url
     {
         return Url::fromPath('icingadb/host/remove-acknowledgement', ['name' => $host->name]);
     }
 
-    public static function scheduleDowntime(Host $host)
+    public static function scheduleDowntime(Host $host): Url
     {
         return Url::fromPath('icingadb/host/schedule-downtime', ['name' => $host->name]);
     }
 
-    public static function sendCustomNotification(Host $host)
+    public static function sendCustomNotification(Host $host): Url
     {
         return Url::fromPath('icingadb/host/send-custom-notification', ['name' => $host->name]);
     }
 
-    public static function processCheckresult(Host $host)
+    public static function processCheckresult(Host $host): Url
     {
         return Url::fromPath('icingadb/host/process-checkresult', ['name' => $host->name]);
     }
 
-    public static function toggleFeatures(Host $host)
+    public static function toggleFeatures(Host $host): Url
     {
         return Url::fromPath('icingadb/host/toggle-features', ['name' => $host->name]);
     }
 
-    public static function services(Host $host)
+    public static function services(Host $host): Url
     {
         return Url::fromPath('icingadb/host/services', ['name' => $host->name]);
     }
diff --git a/library/Icingadb/Common/HostStates.php b/library/Icingadb/Common/HostStates.php
index b74d17bd..ab461ba0 100644
--- a/library/Icingadb/Common/HostStates.php
+++ b/library/Icingadb/Common/HostStates.php
@@ -26,7 +26,7 @@ class HostStates
      *
      * @throws \InvalidArgumentException If the given host state is invalid, i.e. not known
      */
-    public static function int($state)
+    public static function int(string $state): int
     {
         switch (strtolower($state)) {
             case 'up':
@@ -57,7 +57,7 @@ class HostStates
      *
      * @throws \InvalidArgumentException If the given host state is invalid, i.e. not known
      */
-    public static function text($state)
+    public static function text(int $state): string
     {
         switch (true) {
             case $state === self::UP:
@@ -91,7 +91,7 @@ class HostStates
      *
      * @throws \InvalidArgumentException If the given host state is invalid, i.e. not known
      */
-    public static function translated($state)
+    public static function translated(int $state): string
     {
         switch (true) {
             case $state === self::UP:
diff --git a/library/Icingadb/Common/IcingaRedis.php b/library/Icingadb/Common/IcingaRedis.php
index 3a9be148..071c45d8 100644
--- a/library/Icingadb/Common/IcingaRedis.php
+++ b/library/Icingadb/Common/IcingaRedis.php
@@ -41,7 +41,7 @@ class IcingaRedis
      *
      * @throws Exception
      */
-    public function getConnection()
+    public function getConnection(): Redis
     {
         if ($this->redisUnavailable) {
             throw new Exception('Redis is still not available');
@@ -95,6 +95,13 @@ class IcingaRedis
         return $this->redis;
     }
 
+    /**
+     * Get the last icinga heartbeat from redis
+     *
+     * @param Redis|null $redis
+     *
+     * @return ?float|int
+     */
     public static function getLastIcingaHeartbeat(Redis $redis = null)
     {
         if ($redis === null) {
@@ -126,7 +133,15 @@ class IcingaRedis
         return null;
     }
 
-    public static function getPrimaryRedis(Config $moduleConfig = null, Config $redisConfig = null)
+    /**
+     * Get the primary redis instance
+     *
+     * @param Config|null $moduleConfig
+     * @param Config|null $redisConfig
+     *
+     * @return Redis
+     */
+    public static function getPrimaryRedis(Config $moduleConfig = null, Config $redisConfig = null): Redis
     {
         if ($moduleConfig === null) {
             $moduleConfig = Config::module('icingadb');
@@ -149,6 +164,14 @@ class IcingaRedis
         return $redis;
     }
 
+    /**
+     * Get the secondary redis instance if exists
+     *
+     * @param Config|null $moduleConfig
+     * @param Config|null $redisConfig
+     *
+     * @return ?Redis
+     */
     public static function getSecondaryRedis(Config $moduleConfig = null, Config $redisConfig = null)
     {
         if ($moduleConfig === null) {
@@ -177,7 +200,7 @@ class IcingaRedis
         return $redis;
     }
 
-    private static function getTlsParams(Config $config)
+    private static function getTlsParams(Config $config): array
     {
         $config = $config->getSection('redis');
 
diff --git a/library/Icingadb/Common/Links.php b/library/Icingadb/Common/Links.php
index 628b1ee6..5968e5fb 100644
--- a/library/Icingadb/Common/Links.php
+++ b/library/Icingadb/Common/Links.php
@@ -16,127 +16,127 @@ use ipl\Web\Url;
 
 abstract class Links
 {
-    public static function comment(Comment $comment)
+    public static function comment(Comment $comment): Url
     {
         return Url::fromPath('icingadb/comment', ['name' => $comment->name]);
     }
 
-    public static function comments()
+    public static function comments(): Url
     {
         return Url::fromPath('icingadb/comments');
     }
 
-    public static function commentsDelete()
+    public static function commentsDelete(): Url
     {
         return Url::fromPath('icingadb/comments/delete');
     }
 
-    public static function commentsDetails()
+    public static function commentsDetails(): Url
     {
         return Url::fromPath('icingadb/comments/details');
     }
 
-    public static function downtime(Downtime $downtime)
+    public static function downtime(Downtime $downtime): Url
     {
         return Url::fromPath('icingadb/downtime', ['name' => $downtime->name]);
     }
 
-    public static function downtimes()
+    public static function downtimes(): Url
     {
         return Url::fromPath('icingadb/downtimes');
     }
 
-    public static function downtimesDelete()
+    public static function downtimesDelete(): Url
     {
         return Url::fromPath('icingadb/downtimes/delete');
     }
 
-    public static function downtimesDetails()
+    public static function downtimesDetails(): Url
     {
         return Url::fromPath('icingadb/downtimes/details');
     }
 
-    public static function host(Host $host)
+    public static function host(Host $host): Url
     {
         return Url::fromPath('icingadb/host', ['name' => $host->name]);
     }
 
-    public static function hostSource(Host $host)
+    public static function hostSource(Host $host): Url
     {
         return Url::fromPath('icingadb/host/source', ['name' => $host->name]);
     }
 
-    public static function hostsDetails()
+    public static function hostsDetails(): Url
     {
         return Url::fromPath('icingadb/hosts/details');
     }
 
-    public static function hostgroup($hostgroup)
+    public static function hostgroup($hostgroup): Url
     {
         return Url::fromPath('icingadb/hostgroup', ['name' => $hostgroup->name]);
     }
 
-    public static function hosts()
+    public static function hosts(): Url
     {
         return Url::fromPath('icingadb/hosts');
     }
 
-    public static function service(Service $service, Host $host)
+    public static function service(Service $service, Host $host): Url
     {
         return Url::fromPath('icingadb/service', ['name' => $service->name, 'host.name' => $host->name]);
     }
 
-    public static function serviceSource(Service $service, Host $host)
+    public static function serviceSource(Service $service, Host $host): Url
     {
         return Url::fromPath('icingadb/service/source', ['name' => $service->name, 'host.name' => $host->name]);
     }
 
-    public static function servicesDetails()
+    public static function servicesDetails(): Url
     {
         return Url::fromPath('icingadb/services/details');
     }
 
-    public static function servicegroup($servicegroup)
+    public static function servicegroup($servicegroup): Url
     {
         return Url::fromPath('icingadb/servicegroup', ['name' => $servicegroup->name]);
     }
 
-    public static function services()
+    public static function services(): Url
     {
         return Url::fromPath('icingadb/services');
     }
 
-    public static function toggleHostsFeatures()
+    public static function toggleHostsFeatures(): Url
     {
         return Url::fromPath('icingadb/hosts/toggle-features');
     }
 
-    public static function toggleServicesFeatures()
+    public static function toggleServicesFeatures(): Url
     {
         return Url::fromPath('icingadb/services/toggle-features');
     }
 
-    public static function user(User $user)
+    public static function user(User $user): Url
     {
         return Url::fromPath('icingadb/user', ['name' => $user->name]);
     }
 
-    public static function usergroup(Usergroup $usergroup)
+    public static function usergroup(Usergroup $usergroup): Url
     {
         return Url::fromPath('icingadb/usergroup', ['name' => $usergroup->name]);
     }
 
-    public static function users()
+    public static function users(): Url
     {
         return Url::fromPath('icingadb/users');
     }
 
-    public static function usergroups()
+    public static function usergroups(): Url
     {
         return Url::fromPath('icingadb/usergroups');
     }
 
-    public static function event(History $event)
+    public static function event(History $event): Url
     {
         return Url::fromPath('icingadb/event', ['id' => bin2hex($event->id)]);
     }
diff --git a/library/Icingadb/Common/LoadMore.php b/library/Icingadb/Common/LoadMore.php
index 18c9ac23..c9ef0a26 100644
--- a/library/Icingadb/Common/LoadMore.php
+++ b/library/Icingadb/Common/LoadMore.php
@@ -28,7 +28,7 @@ trait LoadMore
      *
      * @return $this
      */
-    public function setPageSize($size)
+    public function setPageSize(int $size): self
     {
         $this->pageSize = $size;
 
@@ -42,7 +42,7 @@ trait LoadMore
      *
      * @return $this
      */
-    public function setPageNumber($number)
+    public function setPageNumber(int $number): self
     {
         $this->pageNumber = $number;
 
@@ -56,7 +56,7 @@ trait LoadMore
      *
      * @return $this
      */
-    public function setLoadMoreUrl(Url $url)
+    public function setLoadMoreUrl(Url $url): self
     {
         $this->loadMoreUrl = $url;
 
@@ -72,7 +72,7 @@ trait LoadMore
      *
      * @return Generator
      */
-    protected function getIterator(ResultSet $result)
+    protected function getIterator(ResultSet $result): Generator
     {
         $count = 0;
         $pageNumber = $this->pageNumber ?: 1;
diff --git a/library/Icingadb/Common/NoSubjectLink.php b/library/Icingadb/Common/NoSubjectLink.php
index eebb88cb..76c9a84d 100644
--- a/library/Icingadb/Common/NoSubjectLink.php
+++ b/library/Icingadb/Common/NoSubjectLink.php
@@ -16,7 +16,7 @@ trait NoSubjectLink
      *
      * @return $this
      */
-    public function setNoSubjectLink($state = true)
+    public function setNoSubjectLink(bool $state = true): self
     {
         $this->noSubjectLink = $state;
 
@@ -28,7 +28,7 @@ trait NoSubjectLink
      *
      * @return bool
      */
-    public function getNoSubjectLink()
+    public function getNoSubjectLink(): bool
     {
         return $this->noSubjectLink;
     }
diff --git a/library/Icingadb/Common/ObjectInspectionDetail.php b/library/Icingadb/Common/ObjectInspectionDetail.php
index 2273bc4d..00258ea4 100644
--- a/library/Icingadb/Common/ObjectInspectionDetail.php
+++ b/library/Icingadb/Common/ObjectInspectionDetail.php
@@ -42,6 +42,11 @@ abstract class ObjectInspectionDetail extends BaseHtmlElement
         $this->joins = $apiResult['joins'];
     }
 
+    /**
+     * Render the object source location
+     *
+     * @return ?array
+     */
     protected function createSourceLocation()
     {
         if (! isset($this->attrs['source_location'])) {
@@ -58,6 +63,11 @@ abstract class ObjectInspectionDetail extends BaseHtmlElement
         ];
     }
 
+    /**
+     * Render object's last check result
+     *
+     * @return ?array
+     */
     protected function createLastCheckResult()
     {
         if (! isset($this->attrs['last_check_result'])) {
@@ -94,7 +104,7 @@ abstract class ObjectInspectionDetail extends BaseHtmlElement
         ];
     }
 
-    protected function createRedisInfo()
+    protected function createRedisInfo(): array
     {
         $title = new HtmlElement('h2', null, Text::create(t('Volatile State Details')));
 
@@ -138,7 +148,7 @@ abstract class ObjectInspectionDetail extends BaseHtmlElement
         )];
     }
 
-    protected function createAttributes()
+    protected function createAttributes(): array
     {
         $blacklist = [
             'name',
@@ -188,6 +198,13 @@ abstract class ObjectInspectionDetail extends BaseHtmlElement
         ];
     }
 
+    /**
+     * Format the given value as a json
+     *
+     * @param  mixed $json
+     *
+     * @return BaseHtmlElement|string
+     */
     private function formatJson($json)
     {
         if (is_scalar($json)) {
@@ -201,7 +218,7 @@ abstract class ObjectInspectionDetail extends BaseHtmlElement
         );
     }
 
-    private function formatTimestamp($ts)
+    private function formatTimestamp($ts): string
     {
         if (empty($ts)) {
             return new EmptyState(t('n. a.'));
@@ -217,22 +234,22 @@ abstract class ObjectInspectionDetail extends BaseHtmlElement
             ->format('Y-m-d\TH:i:s.vP');
     }
 
-    private function formatMillisecondTimestamp($ms)
+    private function formatMillisecondTimestamp($ms): string
     {
         return $this->formatTimestamp($ms / 1000.0);
     }
 
-    private function formatSeconds($s)
+    private function formatSeconds($s): string
     {
         return Format::seconds($s);
     }
 
-    private function formatMilliseconds($ms)
+    private function formatMilliseconds($ms): string
     {
         return Format::seconds($ms / 1000.0);
     }
 
-    private function formatState($state)
+    private function formatState(int $state): string
     {
         switch (true) {
             case $this->object instanceof Host:
@@ -244,7 +261,7 @@ abstract class ObjectInspectionDetail extends BaseHtmlElement
         }
     }
 
-    private function createNameValueTable(array $data, array $formatters)
+    private function createNameValueTable(array $data, array $formatters): Table
     {
         $table = new Table();
         $table->addAttributes(['class' => 'name-value-table']);
diff --git a/library/Icingadb/Common/ObjectLinkDisabled.php b/library/Icingadb/Common/ObjectLinkDisabled.php
index da28e8d3..ca8283f5 100644
--- a/library/Icingadb/Common/ObjectLinkDisabled.php
+++ b/library/Icingadb/Common/ObjectLinkDisabled.php
@@ -16,7 +16,7 @@ trait ObjectLinkDisabled
      *
      * @return $this
      */
-    public function setObjectLinkDisabled($state = true)
+    public function setObjectLinkDisabled(bool $state = true): self
     {
         $this->objectLinkDisabled = $state;
 
@@ -28,7 +28,7 @@ trait ObjectLinkDisabled
      *
      * @return bool
      */
-    public function getObjectLinkDisabled()
+    public function getObjectLinkDisabled(): bool
     {
         return $this->objectLinkDisabled;
     }
diff --git a/library/Icingadb/Common/ServiceLink.php b/library/Icingadb/Common/ServiceLink.php
index 9aa72987..ce83a296 100644
--- a/library/Icingadb/Common/ServiceLink.php
+++ b/library/Icingadb/Common/ServiceLink.php
@@ -6,12 +6,13 @@ namespace Icinga\Module\Icingadb\Common;
 
 use Icinga\Module\Icingadb\Model\Host;
 use Icinga\Module\Icingadb\Model\Service;
+use ipl\Html\FormattedString;
 use ipl\Html\Html;
 use ipl\Web\Widget\StateBall;
 
 trait ServiceLink
 {
-    protected function createServiceLink(Service $service, Host $host, $withStateBall = false)
+    protected function createServiceLink(Service $service, Host $host, bool $withStateBall = false): FormattedString
     {
         $content = [];
 
diff --git a/library/Icingadb/Common/ServiceLinks.php b/library/Icingadb/Common/ServiceLinks.php
index 751796f1..368be48b 100644
--- a/library/Icingadb/Common/ServiceLinks.php
+++ b/library/Icingadb/Common/ServiceLinks.php
@@ -10,7 +10,7 @@ use ipl\Web\Url;
 
 abstract class ServiceLinks
 {
-    public static function acknowledge(Service $service, Host $host)
+    public static function acknowledge(Service $service, Host $host): Url
     {
         return Url::fromPath(
             'icingadb/service/acknowledge',
@@ -18,7 +18,7 @@ abstract class ServiceLinks
         );
     }
 
-    public static function addComment(Service $service, Host $host)
+    public static function addComment(Service $service, Host $host): Url
     {
         return Url::fromPath(
             'icingadb/service/add-comment',
@@ -26,7 +26,7 @@ abstract class ServiceLinks
         );
     }
 
-    public static function checkNow(Service $service, Host $host)
+    public static function checkNow(Service $service, Host $host): Url
     {
         return Url::fromPath(
             'icingadb/service/check-now',
@@ -34,7 +34,7 @@ abstract class ServiceLinks
         );
     }
 
-    public static function scheduleCheck(Service $service, Host $host)
+    public static function scheduleCheck(Service $service, Host $host): Url
     {
         return Url::fromPath(
             'icingadb/service/schedule-check',
@@ -42,7 +42,7 @@ abstract class ServiceLinks
         );
     }
 
-    public static function comments(Service $service, Host $host)
+    public static function comments(Service $service, Host $host): Url
     {
         return Url::fromPath(
             'icingadb/comments',
@@ -50,7 +50,7 @@ abstract class ServiceLinks
         );
     }
 
-    public static function downtimes(Service $service, Host $host)
+    public static function downtimes(Service $service, Host $host): Url
     {
         return Url::fromPath(
             'icingadb/downtimes',
@@ -58,7 +58,7 @@ abstract class ServiceLinks
         );
     }
 
-    public static function history(Service $service, Host $host)
+    public static function history(Service $service, Host $host): Url
     {
         return Url::fromPath(
             'icingadb/service/history',
@@ -66,7 +66,7 @@ abstract class ServiceLinks
         );
     }
 
-    public static function removeAcknowledgement(Service $service, Host $host)
+    public static function removeAcknowledgement(Service $service, Host $host): Url
     {
         return Url::fromPath(
             'icingadb/service/remove-acknowledgement',
@@ -74,7 +74,7 @@ abstract class ServiceLinks
         );
     }
 
-    public static function scheduleDowntime(Service $service, Host $host)
+    public static function scheduleDowntime(Service $service, Host $host): Url
     {
         return Url::fromPath(
             'icingadb/service/schedule-downtime',
@@ -82,7 +82,7 @@ abstract class ServiceLinks
         );
     }
 
-    public static function sendCustomNotification(Service $service, Host $host)
+    public static function sendCustomNotification(Service $service, Host $host): Url
     {
         return Url::fromPath(
             'icingadb/service/send-custom-notification',
@@ -90,7 +90,7 @@ abstract class ServiceLinks
         );
     }
 
-    public static function processCheckresult(Service $service, Host $host)
+    public static function processCheckresult(Service $service, Host $host): Url
     {
         return Url::fromPath(
             'icingadb/service/process-checkresult',
@@ -98,7 +98,7 @@ abstract class ServiceLinks
         );
     }
 
-    public static function toggleFeatures(Service $service, Host $host)
+    public static function toggleFeatures(Service $service, Host $host): Url
     {
         return Url::fromPath(
             'icingadb/service/toggle-features',
diff --git a/library/Icingadb/Common/ServiceStates.php b/library/Icingadb/Common/ServiceStates.php
index c815c1c0..f902eaa5 100644
--- a/library/Icingadb/Common/ServiceStates.php
+++ b/library/Icingadb/Common/ServiceStates.php
@@ -28,7 +28,7 @@ class ServiceStates
      *
      * @throws \InvalidArgumentException If the given service state is invalid, i.e. not known
      */
-    public static function int($state)
+    public static function int(string $state): int
     {
         switch (strtolower($state)) {
             case 'ok':
@@ -62,7 +62,7 @@ class ServiceStates
      *
      * @throws \InvalidArgumentException If the given service state is invalid, i.e. not known
      */
-    public static function text($state)
+    public static function text(int $state): string
     {
         switch (true) {
             case $state === self::OK:
@@ -99,7 +99,7 @@ class ServiceStates
      *
      * @throws \InvalidArgumentException If the given service state is invalid, i.e. not known
      */
-    public static function translated($state)
+    public static function translated(int $state): string
     {
         switch (true) {
             case $state === self::OK:
diff --git a/library/Icingadb/Common/StateBadges.php b/library/Icingadb/Common/StateBadges.php
index a06a38d8..1d6832ad 100644
--- a/library/Icingadb/Common/StateBadges.php
+++ b/library/Icingadb/Common/StateBadges.php
@@ -46,14 +46,14 @@ abstract class StateBadges extends BaseHtmlElement
      *
      * @return Url
      */
-    abstract protected function getBaseUrl();
+    abstract protected function getBaseUrl(): Url;
 
     /**
      * Get the prefix for accessing state information
      *
      * @return string
      */
-    abstract protected function getPrefix();
+    abstract protected function getPrefix(): string;
 
     /**
      * Get the integer of the given state text
@@ -62,14 +62,14 @@ abstract class StateBadges extends BaseHtmlElement
      *
      * @return int
      */
-    abstract protected function getStateInt($state);
+    abstract protected function getStateInt(string $state): int;
 
     /**
      * Get the badge URL
      *
      * @return Url
      */
-    public function getUrl()
+    public function getUrl(): Url
     {
         return $this->url;
     }
@@ -81,7 +81,7 @@ abstract class StateBadges extends BaseHtmlElement
      *
      * @return $this
      */
-    public function setUrl($url)
+    public function setUrl(Url $url): self
     {
         $this->url = $url;
 
@@ -96,7 +96,7 @@ abstract class StateBadges extends BaseHtmlElement
      *
      * @return Link
      */
-    public function createLink($content, array $params = null)
+    public function createLink($content, array $params = null): Link
     {
         $url = clone $this->getUrl();
 
@@ -111,7 +111,14 @@ abstract class StateBadges extends BaseHtmlElement
         return new Link($content, $url);
     }
 
-    protected function createBadge($state)
+    /**
+     * Create a state bade
+     *
+     * @param string $state
+     *
+     * @return ?BaseHtmlElement
+     */
+    protected function createBadge(string $state)
     {
         $key = $this->prefix . "_{$state}";
 
@@ -125,7 +132,14 @@ abstract class StateBadges extends BaseHtmlElement
         return null;
     }
 
-    protected function createGroup($state)
+    /**
+     * Create a state group
+     *
+     * @param string $state
+     *
+     * @return ?BaseHtmlElement
+     */
+    protected function createGroup(string $state)
     {
         $content = [];
         $handledKey = $this->prefix . "_{$state}_handled";
diff --git a/library/Icingadb/Common/ViewMode.php b/library/Icingadb/Common/ViewMode.php
index 744ad9be..841f28b1 100644
--- a/library/Icingadb/Common/ViewMode.php
+++ b/library/Icingadb/Common/ViewMode.php
@@ -12,7 +12,7 @@ trait ViewMode
     /**
      * Get the view mode
      *
-     * @return string
+     * @return ?string
      */
     public function getViewMode()
     {
@@ -26,7 +26,7 @@ trait ViewMode
      *
      * @return $this
      */
-    public function setViewMode($viewMode)
+    public function setViewMode(string $viewMode): self
     {
         $this->viewMode = $viewMode;
 
diff --git a/library/Icingadb/Compat/CompatObject.php b/library/Icingadb/Compat/CompatObject.php
index f01fce82..f7ef06e5 100644
--- a/library/Icingadb/Compat/CompatObject.php
+++ b/library/Icingadb/Compat/CompatObject.php
@@ -51,17 +51,17 @@ trait CompatObject
      *
      * @return string
      */
-    public function getName()
+    public function getName(): string
     {
         return $this->object->name;
     }
 
-    public function fetch()
+    public function fetch(): bool
     {
         return true;
     }
 
-    protected function fetchRawCustomvars()
+    protected function fetchRawCustomvars(): self
     {
         if ($this->rawCustomvars !== null) {
             return $this;
@@ -79,7 +79,7 @@ trait CompatObject
         return $this;
     }
 
-    public function fetchCustomvars()
+    public function fetchCustomvars(): self
     {
         if ($this->customvars !== null) {
             return $this;
@@ -181,6 +181,13 @@ trait CompatObject
         throw new NotImplementedError('getDataView() is not supported');
     }
 
+    /**
+     * Get the bool type of the given value as an int
+     *
+     * @param bool|string $value
+     *
+     * @return ?int
+     */
     private function getBoolType($value)
     {
         switch ($value) {
diff --git a/library/Icingadb/Compat/CompatService.php b/library/Icingadb/Compat/CompatService.php
index 8045b604..cb5f15ee 100644
--- a/library/Icingadb/Compat/CompatService.php
+++ b/library/Icingadb/Compat/CompatService.php
@@ -143,7 +143,7 @@ class CompatService extends Service
      *
      * @return CompatHost
      */
-    public function getHost()
+    public function getHost(): CompatHost
     {
         if ($this->host === null) {
             $this->host = new CompatHost($this->object->host);
diff --git a/library/Icingadb/Compat/UrlMigrator.php b/library/Icingadb/Compat/UrlMigrator.php
index cc58cc8d..4b06ef86 100644
--- a/library/Icingadb/Compat/UrlMigrator.php
+++ b/library/Icingadb/Compat/UrlMigrator.php
@@ -39,18 +39,18 @@ class UrlMigrator
         'monitoring/tactical' => ['services', 'icingadb/tactical']
     ];
 
-    public static function isSupportedUrl(Url $url)
+    public static function isSupportedUrl(Url $url): bool
     {
         $supportedPaths = self::SUPPORTED_PATHS;
         return isset($supportedPaths[$url->getPath()]);
     }
 
-    public static function hasQueryTransformer($name)
+    public static function hasQueryTransformer(string $name): bool
     {
         return method_exists(new self(), $name . 'Columns');
     }
 
-    public static function transformUrl(Url $url)
+    public static function transformUrl(Url $url): Url
     {
         if (! self::isSupportedUrl($url)) {
             throw new InvalidArgumentException(sprintf('Url path "%s" is not supported', $url->getPath()));
@@ -70,7 +70,15 @@ class UrlMigrator
         return $url;
     }
 
-    public static function transformFilter(Filter\Rule $filter, $queryTransformer = null)
+    /**
+     * Transform the given legacy filter
+     *
+     * @param Filter\Rule $filter
+     * @param string|null $queryTransformer
+     *
+     * @return Filter\Rule|false
+     */
+    public static function transformFilter(Filter\Rule $filter, string $queryTransformer = null)
     {
         $transformer = new self();
 
@@ -87,6 +95,15 @@ class UrlMigrator
         return $rewritten === false ? false : ($rewritten instanceof Filter\Rule ? $rewritten : $filter);
     }
 
+    /**
+     * Rewrite the given filter and legacy columns
+     *
+     * @param Filter\Rule $filter
+     * @param array $legacyColumns
+     * @param Filter\Chain|null $parent
+     *
+     * @return ?mixed
+     */
     protected function rewrite(Filter\Rule $filter, array $legacyColumns, Filter\Chain $parent = null)
     {
         $rewritten = null;
@@ -174,7 +191,7 @@ class UrlMigrator
         return $rewritten;
     }
 
-    protected static function commonColumns()
+    protected static function commonColumns(): array
     {
         return [
 
@@ -222,7 +239,7 @@ class UrlMigrator
         ];
     }
 
-    protected static function hostsColumns()
+    protected static function hostsColumns(): array
     {
         return [
 
@@ -402,7 +419,7 @@ class UrlMigrator
         ];
     }
 
-    protected static function multipleHostsColumns()
+    protected static function multipleHostsColumns(): array
     {
         return array_merge(
             static::hostsColumns(),
@@ -414,7 +431,7 @@ class UrlMigrator
         );
     }
 
-    protected static function hostColumns()
+    protected static function hostColumns(): array
     {
         return [
             'host' => [
@@ -423,7 +440,7 @@ class UrlMigrator
         ];
     }
 
-    protected static function servicesColumns()
+    protected static function servicesColumns(): array
     {
         return [
 
@@ -723,7 +740,7 @@ class UrlMigrator
         ];
     }
 
-    protected static function multipleServicesColumns()
+    protected static function multipleServicesColumns(): array
     {
         return array_merge(
             static::servicesColumns(),
@@ -738,7 +755,7 @@ class UrlMigrator
         );
     }
 
-    protected static function serviceColumns()
+    protected static function serviceColumns(): array
     {
         return [
             'host' => [
@@ -750,7 +767,7 @@ class UrlMigrator
         ];
     }
 
-    protected static function hostgroupsColumns()
+    protected static function hostgroupsColumns(): array
     {
         return [
 
@@ -772,7 +789,7 @@ class UrlMigrator
         ];
     }
 
-    protected static function servicegroupsColumns()
+    protected static function servicegroupsColumns(): array
     {
         return [
 
@@ -799,7 +816,7 @@ class UrlMigrator
         ];
     }
 
-    protected static function contactgroupsColumns()
+    protected static function contactgroupsColumns(): array
     {
         return [
 
@@ -819,7 +836,7 @@ class UrlMigrator
         ];
     }
 
-    protected static function contactsColumns()
+    protected static function contactsColumns(): array
     {
         $receivesStateNotifications = function ($state, $type = null) {
             return function ($filter) use ($state, $type) {
@@ -939,7 +956,7 @@ class UrlMigrator
         ];
     }
 
-    protected static function commentsColumns()
+    protected static function commentsColumns(): array
     {
         return [
 
@@ -986,7 +1003,7 @@ class UrlMigrator
         ];
     }
 
-    protected static function downtimesColumns()
+    protected static function downtimesColumns(): array
     {
         return [
 
@@ -1054,7 +1071,7 @@ class UrlMigrator
         ];
     }
 
-    protected static function historyColumns()
+    protected static function historyColumns(): array
     {
         return [
 
@@ -1117,7 +1134,7 @@ class UrlMigrator
         ];
     }
 
-    protected static function notificationHistoryColumns()
+    protected static function notificationHistoryColumns(): array
     {
         return [
 
diff --git a/library/Icingadb/Data/PivotTable.php b/library/Icingadb/Data/PivotTable.php
index 28320080..31ccd4e7 100644
--- a/library/Icingadb/Data/PivotTable.php
+++ b/library/Icingadb/Data/PivotTable.php
@@ -98,7 +98,7 @@ class PivotTable
      * @param   string      $yAxisColumn    Y-axis pivot column
      * @param   array      $gridcols        Grid columns
      */
-    public function __construct(Query $query, $xAxisColumn, $yAxisColumn, $gridcols)
+    public function __construct(Query $query, string $xAxisColumn, string $yAxisColumn, array $gridcols)
     {
         foreach ($query->getOrderBy() as $sort) {
             $this->order[$sort[0]] = $sort[1];
@@ -118,7 +118,7 @@ class PivotTable
      *
      * @return  $this
      */
-    public function setXAxisFilter(Filter\Rule $filter = null)
+    public function setXAxisFilter(Filter\Rule $filter = null): self
     {
         $this->xAxisFilter = $filter;
         return  $this;
@@ -127,11 +127,11 @@ class PivotTable
     /**
      * Set the filter to apply on the query for the y-axis
      *
-     * @param   Filter  $filter
+     * @param   Filter\Rule  $filter
      *
      * @return  $this
      */
-    public function setYAxisFilter(Filter\Rule $filter = null)
+    public function setYAxisFilter(Filter\Rule $filter = null): self
     {
         $this->yAxisFilter = $filter;
         return  $this;
@@ -144,8 +144,14 @@ class PivotTable
      *
      * @return string
      */
-    public function getXAxisHeader()
+    public function getXAxisHeader(): string
     {
+        if ($this->xAxisHeader === null && $this->xAxisColumn === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->xAxisHeader !== null ? $this->xAxisHeader : $this->xAxisColumn;
     }
 
@@ -156,9 +162,9 @@ class PivotTable
      *
      * @return  $this
      */
-    public function setXAxisHeader($xAxisHeader)
+    public function setXAxisHeader(string $xAxisHeader): self
     {
-        $this->xAxisHeader = (string) $xAxisHeader;
+        $this->xAxisHeader = $xAxisHeader;
         return $this;
     }
 
@@ -169,8 +175,14 @@ class PivotTable
      *
      * @return string
      */
-    public function getYAxisHeader()
+    public function getYAxisHeader(): string
     {
+        if ($this->yAxisHeader === null && $this->yAxisColumn === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->yAxisHeader !== null ? $this->yAxisHeader : $this->yAxisColumn;
     }
 
@@ -181,9 +193,9 @@ class PivotTable
      *
      * @return  $this
      */
-    public function setYAxisHeader($yAxisHeader)
+    public function setYAxisHeader(string $yAxisHeader): self
     {
-        $this->yAxisHeader = (string) $yAxisHeader;
+        $this->yAxisHeader = $yAxisHeader;
         return $this;
     }
 
@@ -196,7 +208,7 @@ class PivotTable
      *
      * @return  int
      */
-    protected function getPaginationParameter($axis, $param, $default = null)
+    protected function getPaginationParameter(string $axis, string $param, int $default = null): int
     {
         $request = Icinga::app()->getRequest();
 
@@ -214,7 +226,7 @@ class PivotTable
      *
      * @return Query
      */
-    protected function queryXAxis()
+    protected function queryXAxis(): Query
     {
         if ($this->xAxisQuery === null) {
             $this->xAxisQuery = clone $this->baseQuery;
@@ -263,7 +275,7 @@ class PivotTable
      *
      * @return Query
      */
-    protected function queryYAxis()
+    protected function queryYAxis(): Query
     {
         if ($this->yAxisQuery === null) {
             $this->yAxisQuery = clone $this->baseQuery;
@@ -317,7 +329,7 @@ class PivotTable
      *
      * @return  Paginatable
      */
-    public function paginateXAxis($limit = null, $page = null)
+    public function paginateXAxis(int $limit = null, int $page = null): Paginatable
     {
         if ($limit === null || $page === null) {
             if ($limit === null) {
@@ -348,7 +360,7 @@ class PivotTable
      *
      * @return  Paginatable
      */
-    public function paginateYAxis($limit = null, $page = null)
+    public function paginateYAxis(int $limit = null, int $page = null): Paginatable
     {
         if ($limit === null || $page === null) {
             if ($limit === null) {
@@ -372,7 +384,7 @@ class PivotTable
      *
      * @return array
      */
-    public function toArray()
+    public function toArray(): array
     {
         if (
             ($this->xAxisFilter === null && $this->yAxisFilter === null)
diff --git a/library/Icingadb/Hook/TabHook/HookActions.php b/library/Icingadb/Hook/TabHook/HookActions.php
index e7c40bf4..c407657e 100644
--- a/library/Icingadb/Hook/TabHook/HookActions.php
+++ b/library/Icingadb/Hook/TabHook/HookActions.php
@@ -29,7 +29,7 @@ trait HookActions
      *
      * @return ValidHtml[]
      */
-    abstract protected function getDefaultTabControls();
+    abstract protected function getDefaultTabControls(): array;
 
     public function __call($methodName, $args)
     {
@@ -50,6 +50,8 @@ trait HookActions
      * Register the object for which to load additional tabs
      *
      * @param Model $object
+     *
+     * @return void
      */
     protected function loadTabsForObject(Model $object)
     {
@@ -103,6 +105,8 @@ trait HookActions
      * Render the given tab hook
      *
      * @param TabHook $hook
+     *
+     * @return void
      */
     protected function showTabHook(TabHook $hook)
     {
diff --git a/library/Icingadb/Model/Behavior/ReRoute.php b/library/Icingadb/Model/Behavior/ReRoute.php
index 0961fd64..197b06cf 100644
--- a/library/Icingadb/Model/Behavior/ReRoute.php
+++ b/library/Icingadb/Model/Behavior/ReRoute.php
@@ -16,7 +16,7 @@ class ReRoute implements RewriteBehavior
         $this->routes = $routes;
     }
 
-    public function getRoutes()
+    public function getRoutes(): array
     {
         return $this->routes;
     }
diff --git a/library/Icingadb/Model/CustomvarFlat.php b/library/Icingadb/Model/CustomvarFlat.php
index 43fab0b3..e63f9581 100644
--- a/library/Icingadb/Model/CustomvarFlat.php
+++ b/library/Icingadb/Model/CustomvarFlat.php
@@ -85,7 +85,7 @@ class CustomvarFlat extends Model
      *
      * @return array
      */
-    public function unFlattenVars(Traversable $flattenedVars)
+    public function unFlattenVars(Traversable $flattenedVars): array
     {
         $registerValue = function (&$data, $path, $value) use (&$registerValue) {
             $step = array_shift($path);
diff --git a/library/Icingadb/Model/HostState.php b/library/Icingadb/Model/HostState.php
index 11e25533..2da7d779 100644
--- a/library/Icingadb/Model/HostState.php
+++ b/library/Icingadb/Model/HostState.php
@@ -71,7 +71,7 @@ class HostState extends State
      *
      * @return string
      */
-    public function getStateText()
+    public function getStateText(): string
     {
         return HostStates::text($this->soft_state);
     }
@@ -81,7 +81,7 @@ class HostState extends State
      *
      * @return string
      */
-    public function getStateTextTranslated()
+    public function getStateTextTranslated(): string
     {
         return HostStates::text($this->soft_state);
     }
diff --git a/library/Icingadb/Model/ServiceState.php b/library/Icingadb/Model/ServiceState.php
index 0124fa82..48bb9ec0 100644
--- a/library/Icingadb/Model/ServiceState.php
+++ b/library/Icingadb/Model/ServiceState.php
@@ -68,7 +68,7 @@ class ServiceState extends State
      *
      * @return string
      */
-    public function getStateText()
+    public function getStateText(): string
     {
         return ServiceStates::text($this->soft_state);
     }
@@ -78,7 +78,7 @@ class ServiceState extends State
      *
      * @return string
      */
-    public function getStateTextTranslated()
+    public function getStateTextTranslated(): string
     {
         return ServiceStates::text($this->soft_state);
     }
diff --git a/library/Icingadb/ProvidedHook/IcingaHealth.php b/library/Icingadb/ProvidedHook/IcingaHealth.php
index ab85a37f..bb584d46 100644
--- a/library/Icingadb/ProvidedHook/IcingaHealth.php
+++ b/library/Icingadb/ProvidedHook/IcingaHealth.php
@@ -16,12 +16,12 @@ class IcingaHealth extends HealthHook
     /** @var Instance */
     protected $instance;
 
-    public function getName()
+    public function getName(): string
     {
         return 'Icinga DB';
     }
 
-    public function getUrl()
+    public function getUrl(): Url
     {
         return Url::fromPath('icingadb/health');
     }
@@ -57,7 +57,7 @@ class IcingaHealth extends HealthHook
         }
     }
 
-    protected function getInstance()
+    protected function getInstance(): Instance
     {
         if ($this->instance === null) {
             $this->instance = Instance::on($this->getDb())
diff --git a/library/Icingadb/ProvidedHook/RedisHealth.php b/library/Icingadb/ProvidedHook/RedisHealth.php
index ad8f8f59..0c9fc9fd 100644
--- a/library/Icingadb/ProvidedHook/RedisHealth.php
+++ b/library/Icingadb/ProvidedHook/RedisHealth.php
@@ -14,7 +14,7 @@ class RedisHealth extends HealthHook
 {
     use Database;
 
-    public function getName()
+    public function getName(): string
     {
         return 'Icinga Redis';
     }
diff --git a/library/Icingadb/ProvidedHook/X509/Sni.php b/library/Icingadb/ProvidedHook/X509/Sni.php
index 51d6493f..d6e1415b 100644
--- a/library/Icingadb/ProvidedHook/X509/Sni.php
+++ b/library/Icingadb/ProvidedHook/X509/Sni.php
@@ -4,6 +4,7 @@
 
 namespace Icinga\Module\Icingadb\ProvidedHook\X509;
 
+use Generator;
 use Icinga\Data\Filter\Filter;
 use Icinga\Module\Icingadb\Common\Auth;
 use Icinga\Module\Icingadb\Common\Database;
@@ -19,7 +20,7 @@ class Sni extends SniHook
     /**
      * @inheritDoc
      */
-    public function getHosts(Filter $filter = null)
+    public function getHosts(Filter $filter = null): Generator
     {
         $queryHost = Host::on($this->getDb());
 
diff --git a/library/Icingadb/Redis/VolatileState.php b/library/Icingadb/Redis/VolatileState.php
index 055f36b1..d15b00a3 100644
--- a/library/Icingadb/Redis/VolatileState.php
+++ b/library/Icingadb/Redis/VolatileState.php
@@ -48,7 +48,7 @@ class VolatileState
      *
      * @return $this
      */
-    public function fetch(State $state)
+    public function fetch(State $state): self
     {
         $type = substr($state->getTableName(), 0, -6);
 
diff --git a/library/Icingadb/Setup/ApiTransportPage.php b/library/Icingadb/Setup/ApiTransportPage.php
index 236c30a6..310933ae 100644
--- a/library/Icingadb/Setup/ApiTransportPage.php
+++ b/library/Icingadb/Setup/ApiTransportPage.php
@@ -96,7 +96,7 @@ class ApiTransportPage extends Form
         return true;
     }
 
-    protected function validateConfiguration()
+    protected function validateConfiguration(): bool
     {
         try {
             CommandTransport::createTransport(new ConfigObject($this->getValues()))->probe();
diff --git a/library/Icingadb/Setup/DbResourcePage.php b/library/Icingadb/Setup/DbResourcePage.php
index fee7619a..8836c6fc 100644
--- a/library/Icingadb/Setup/DbResourcePage.php
+++ b/library/Icingadb/Setup/DbResourcePage.php
@@ -95,7 +95,7 @@ class DbResourcePage extends Form
         return true;
     }
 
-    protected function validateConfiguration($showLog = false)
+    protected function validateConfiguration(bool $showLog = false): bool
     {
         $inspection = ResourceConfigForm::inspectResource($this);
         if ($inspection !== null) {
diff --git a/library/Icingadb/Util/FeatureStatus.php b/library/Icingadb/Util/FeatureStatus.php
index 7e22860a..94bf6d47 100644
--- a/library/Icingadb/Util/FeatureStatus.php
+++ b/library/Icingadb/Util/FeatureStatus.php
@@ -9,7 +9,7 @@ use Icinga\Module\Icingadb\Command\Object\ToggleObjectFeatureCommand;
 
 class FeatureStatus extends ArrayObject
 {
-    public function __construct($type, $summary)
+    public function __construct(string $type, $summary)
     {
         $prefix = "{$type}s";
 
@@ -29,7 +29,7 @@ class FeatureStatus extends ArrayObject
         parent::__construct($featureStatus, ArrayObject::ARRAY_AS_PROPS);
     }
 
-    protected function getFeatureStatus($feature, $prefix, $summary)
+    protected function getFeatureStatus(string $feature, string $prefix, $summary): int
     {
         $key = "{$prefix}_{$feature}";
         $value = (int) $summary->$key;
diff --git a/library/Icingadb/Util/PerfData.php b/library/Icingadb/Util/PerfData.php
index 8f456e34..6a6f6591 100644
--- a/library/Icingadb/Util/PerfData.php
+++ b/library/Icingadb/Util/PerfData.php
@@ -77,7 +77,7 @@ class PerfData
      * @param   string      $label      The perfdata label
      * @param   string      $value      The perfdata value
      */
-    public function __construct($label, $value)
+    public function __construct(string $label, string $value)
     {
         $this->perfdataValue = $value;
         $this->label = $label;
@@ -111,7 +111,7 @@ class PerfData
      *
      * @throws  InvalidArgumentException    In case the given performance data has no content or a invalid format
      */
-    public static function fromString($perfdata)
+    public static function fromString(string $perfdata): self
     {
         if (empty($perfdata)) {
             throw new InvalidArgumentException('PerfData::fromString expects a string with content');
@@ -130,7 +130,7 @@ class PerfData
      *
      * @return  bool    True in case it's a number, otherwise False
      */
-    public function isNumber()
+    public function isNumber(): bool
     {
         return $this->unit === null;
     }
@@ -140,7 +140,7 @@ class PerfData
      *
      * @return  bool    True in case it's seconds, otherwise False
      */
-    public function isSeconds()
+    public function isSeconds(): bool
     {
         return $this->unit === 's';
     }
@@ -150,7 +150,7 @@ class PerfData
      *
      * @return  bool    True in case it's temperature, otherwise False
      */
-    public function isTemperature()
+    public function isTemperature(): bool
     {
         return in_array($this->unit, array('C', 'F', 'K'));
     }
@@ -160,7 +160,7 @@ class PerfData
      *
      * @return  bool    True in case it's in percentage, otherwise False
      */
-    public function isPercentage()
+    public function isPercentage(): bool
     {
         return $this->unit === '%';
     }
@@ -170,7 +170,7 @@ class PerfData
      *
      * @return bool   True in case it's in packets
      */
-    public function isPackets()
+    public function isPackets(): bool
     {
         return $this->unit === 'packets';
     }
@@ -180,7 +180,7 @@ class PerfData
      *
      * @return bool
      */
-    public function isLumens()
+    public function isLumens(): bool
     {
         return $this->unit === 'lm';
     }
@@ -190,7 +190,7 @@ class PerfData
      *
      * @return bool
      */
-    public function isDecibelMilliWatts()
+    public function isDecibelMilliWatts(): bool
     {
         return $this->unit === 'dBm';
     }
@@ -200,7 +200,7 @@ class PerfData
      *
      * @return bool
      */
-    public function isBits()
+    public function isBits(): bool
     {
         return $this->unit === 'b';
     }
@@ -210,7 +210,7 @@ class PerfData
      *
      * @return  bool    True in case it's in bytes, otherwise False
      */
-    public function isBytes()
+    public function isBytes(): bool
     {
         return $this->unit === 'B';
     }
@@ -220,7 +220,7 @@ class PerfData
      *
      * @return bool
      */
-    public function isWattHours()
+    public function isWattHours(): bool
     {
         return $this->unit === 'Wh';
     }
@@ -230,7 +230,7 @@ class PerfData
      *
      * @return bool
      */
-    public function isWatts()
+    public function isWatts(): bool
     {
         return $this->unit === 'W';
     }
@@ -240,7 +240,7 @@ class PerfData
      *
      * @return bool
      */
-    public function isAmperes()
+    public function isAmperes(): bool
     {
         return $this->unit === 'A';
     }
@@ -250,7 +250,7 @@ class PerfData
      *
      * @return bool
      */
-    public function isAmpSeconds()
+    public function isAmpSeconds(): bool
     {
         return $this->unit === 'As';
     }
@@ -260,7 +260,7 @@ class PerfData
      *
      * @return bool
      */
-    public function isVolts()
+    public function isVolts(): bool
     {
         return $this->unit === 'V';
     }
@@ -270,7 +270,7 @@ class PerfData
      *
      * @return bool
      */
-    public function isOhms()
+    public function isOhms(): bool
     {
         return $this->unit === 'O';
     }
@@ -280,7 +280,7 @@ class PerfData
      *
      * @return bool
      */
-    public function isGrams()
+    public function isGrams(): bool
     {
         return $this->unit === 'g';
     }
@@ -290,7 +290,7 @@ class PerfData
      *
      * @return bool
      */
-    public function isLiters()
+    public function isLiters(): bool
     {
         return $this->unit === 'l';
     }
@@ -300,7 +300,7 @@ class PerfData
      *
      * @return  bool    True in case it's a counter, otherwise False
      */
-    public function isCounter()
+    public function isCounter(): bool
     {
         return $this->unit === 'c';
     }
@@ -310,7 +310,7 @@ class PerfData
      *
      * @return  bool    True when the perfdata is visualizable
      */
-    public function isVisualizable()
+    public function isVisualizable(): bool
     {
         return isset($this->minValue) && isset($this->maxValue) && isset($this->value);
     }
@@ -318,7 +318,7 @@ class PerfData
     /**
      * Return this perfomance data's label
      */
-    public function getLabel()
+    public function getLabel(): string
     {
         return $this->label;
     }
@@ -336,7 +336,7 @@ class PerfData
     /**
      * Return the unit as a string
      *
-     * @return string
+     * @return ?string
      */
     public function getUnit()
     {
@@ -371,7 +371,7 @@ class PerfData
      *
      * @return  ThresholdRange
      */
-    public function getWarningThreshold()
+    public function getWarningThreshold(): ThresholdRange
     {
         return $this->warningThreshold;
     }
@@ -381,7 +381,7 @@ class PerfData
      *
      * @return  ThresholdRange
      */
-    public function getCriticalThreshold()
+    public function getCriticalThreshold(): ThresholdRange
     {
         return $this->criticalThreshold;
     }
@@ -389,7 +389,7 @@ class PerfData
     /**
      * Return the minimum value or null if it is not available
      *
-     * @return  null|string
+     * @return ?float
      */
     public function getMinimumValue()
     {
@@ -460,7 +460,7 @@ class PerfData
         }
     }
 
-    protected function calculatePieChartData()
+    protected function calculatePieChartData(): array
     {
         $rawValue = $this->getValue();
         $minValue = $this->getMinimumValue() !== null ? $this->getMinimumValue() : 0;
@@ -482,7 +482,7 @@ class PerfData
     }
 
 
-    public function asInlinePie()
+    public function asInlinePie(): InlinePie
     {
         if (! $this->isVisualizable()) {
             throw new LogicException('Cannot calculate piechart data for unvisualizable perfdata entry.');
@@ -560,7 +560,7 @@ class PerfData
      *
      * @return string
      */
-    public function formatLabel($html = false)
+    public function formatLabel(bool $html = false): string
     {
         return sprintf(
             $html ? '<b>%s %s</b> (%s%%)' : '%s %s (%s%%)',
@@ -570,7 +570,7 @@ class PerfData
         );
     }
 
-    public function toArray()
+    public function toArray(): array
     {
         return array(
             'label' => $this->getLabel(),
@@ -591,7 +591,7 @@ class PerfData
      *
      * @return int
      */
-    public function getState()
+    public function getState(): int
     {
         if ($this->value === null) {
             return ServiceStates::UNKNOWN;
@@ -617,7 +617,7 @@ class PerfData
      *
      * @return bool
      */
-    public function worseThan(PerfData $rhs)
+    public function worseThan(PerfData $rhs): bool
     {
         if (($state = $this->getState()) === ($rhsState = $rhs->getState())) {
             return $this->getPercentage() > $rhs->getPercentage();
diff --git a/library/Icingadb/Util/PerfDataFormat.php b/library/Icingadb/Util/PerfDataFormat.php
index 4789dd53..5ff11fa5 100644
--- a/library/Icingadb/Util/PerfDataFormat.php
+++ b/library/Icingadb/Util/PerfDataFormat.php
@@ -56,7 +56,7 @@ class PerfDataFormat
 
     protected static $secondPrefix = [-3 => 'ns', -2 => 'µs', -1 => 'ms', 's'];
 
-    public static function getInstance()
+    public static function getInstance(): self
     {
         if (self::$instance === null) {
             self::$instance = new PerfDataFormat();
@@ -65,57 +65,57 @@ class PerfDataFormat
         return self::$instance;
     }
 
-    public static function bits($value)
+    public static function bits($value): string
     {
         return self::formatForUnits($value, self::$bitPrefix, self::$generalBase);
     }
 
-    public static function bytes($value)
+    public static function bytes($value): string
     {
         return self::formatForUnits($value, self::$bytePrefix, self::$generalBase);
     }
 
-    public static function wattHours($value)
+    public static function wattHours($value): string
     {
         return self::formatForUnits($value, self::$wattHourPrefix, self::$generalBase);
     }
 
-    public static function watts($value)
+    public static function watts($value): string
     {
         return self::formatForUnits($value, self::$wattPrefix, self::$generalBase);
     }
 
-    public static function amperes($value)
+    public static function amperes($value): string
     {
         return self::formatForUnits($value, self::$amperePrefix, self::$generalBase);
     }
 
-    public static function ampereSeconds($value)
+    public static function ampereSeconds($value): string
     {
         return self::formatForUnits($value, self::$ampSecondPrefix, self::$generalBase);
     }
 
-    public static function volts($value)
+    public static function volts($value): string
     {
         return self::formatForUnits($value, self::$voltPrefix, self::$generalBase);
     }
 
-    public static function ohms($value)
+    public static function ohms($value): string
     {
         return self::formatForUnits($value, self::$ohmPrefix, self::$generalBase);
     }
 
-    public static function grams($value)
+    public static function grams($value): string
     {
         return self::formatForUnits($value, self::$gramPrefix, self::$generalBase);
     }
 
-    public static function liters($value)
+    public static function liters($value): string
     {
         return self::formatForUnits($value, self::$literPrefix, self::$generalBase);
     }
 
-    public static function seconds($value)
+    public static function seconds($value): string
     {
         $absValue = abs($value);
 
@@ -130,7 +130,7 @@ class PerfDataFormat
         return sprintf('%0.2f d', $value / 86400);
     }
 
-    protected static function formatForUnits($value, &$units, $base)
+    protected static function formatForUnits($value, array &$units, int $base): string
     {
         $sign = '';
         if ($value < 0) {
diff --git a/library/Icingadb/Util/PerfDataSet.php b/library/Icingadb/Util/PerfDataSet.php
index 63a73cb3..921bb56e 100644
--- a/library/Icingadb/Util/PerfDataSet.php
+++ b/library/Icingadb/Util/PerfDataSet.php
@@ -35,7 +35,7 @@ class PerfDataSet implements IteratorAggregate
      *
      * @param   string      $perfdataStr    A space separated list of label/value pairs
      */
-    protected function __construct($perfdataStr)
+    protected function __construct(string $perfdataStr)
     {
         if (($perfdataStr = trim($perfdataStr)) !== '') {
             $this->perfdataStr = $perfdataStr;
@@ -48,7 +48,7 @@ class PerfDataSet implements IteratorAggregate
      *
      * @return  ArrayIterator
      */
-    public function getIterator()
+    public function getIterator(): ArrayIterator
     {
         return new ArrayIterator($this->asArray());
     }
@@ -60,7 +60,7 @@ class PerfDataSet implements IteratorAggregate
      *
      * @return  PerfDataSet
      */
-    public static function fromString($perfdataStr)
+    public static function fromString(string $perfdataStr): self
     {
         return new static($perfdataStr);
     }
@@ -70,7 +70,7 @@ class PerfDataSet implements IteratorAggregate
      *
      * @return  array
      */
-    public function asArray()
+    public function asArray(): array
     {
         return $this->perfdata;
     }
@@ -95,7 +95,7 @@ class PerfDataSet implements IteratorAggregate
      *
      * @return  string      The label found
      */
-    protected function readLabel()
+    protected function readLabel(): string
     {
         $this->skipSpaces();
         if (in_array($this->perfdataStr[$this->parserPos], array('"', "'"))) {
@@ -122,7 +122,7 @@ class PerfDataSet implements IteratorAggregate
      *
      * @return  string
      */
-    protected function readUntil($stopChar)
+    protected function readUntil(string $stopChar): string
     {
         $start = $this->parserPos;
         while ($this->parserPos < strlen($this->perfdataStr) && $this->perfdataStr[$this->parserPos] !== $stopChar) {
diff --git a/library/Icingadb/Util/PluginOutput.php b/library/Icingadb/Util/PluginOutput.php
index 4d822636..8b1f82d0 100644
--- a/library/Icingadb/Util/PluginOutput.php
+++ b/library/Icingadb/Util/PluginOutput.php
@@ -193,7 +193,7 @@ class PluginOutput extends HtmlString
      * @todo Do we really need to create a DOM here? Or is a preg_replace like we do it for text also feasible?
      * @return  string
      */
-    protected function processHtml($html)
+    protected function processHtml(string $html): string
     {
         $pattern = '/[([](OK|WARNING|CRITICAL|UNKNOWN|UP|DOWN)[)\]]/';
         $doc = new DOMDocument();
diff --git a/library/Icingadb/Util/ThresholdRange.php b/library/Icingadb/Util/ThresholdRange.php
index ed7d1c12..c92842d0 100644
--- a/library/Icingadb/Util/ThresholdRange.php
+++ b/library/Icingadb/Util/ThresholdRange.php
@@ -44,7 +44,7 @@ class ThresholdRange
      *
      * @return  ThresholdRange
      */
-    public static function fromString($rawRange)
+    public static function fromString(string $rawRange): self
     {
         $range = new static();
         $range->raw = $rawRange;
@@ -92,7 +92,7 @@ class ThresholdRange
      *
      * @return  $this
      */
-    public function setMin($min)
+    public function setMin(float $min): self
     {
         $this->min = $min;
         return $this;
@@ -115,7 +115,7 @@ class ThresholdRange
      *
      * @return  $this
      */
-    public function setMax($max)
+    public function setMax(float $max): self
     {
         $this->max = $max;
         return $this;
@@ -138,7 +138,7 @@ class ThresholdRange
      *
      * @return  $this
      */
-    public function setInverted($inverted = true)
+    public function setInverted(bool $inverted = true): self
     {
         $this->inverted = $inverted;
         return $this;
@@ -149,7 +149,7 @@ class ThresholdRange
      *
      * @return  bool
      */
-    public function isInverted()
+    public function isInverted(): bool
     {
         return $this->inverted;
     }
@@ -161,7 +161,7 @@ class ThresholdRange
      *
      * @return  bool
      */
-    public function contains($value)
+    public function contains(float $value): bool
     {
         return (bool) ($this->inverted ^ (
             ($this->min === null || $this->min <= $value) && ($this->max === null || $this->max >= $value)
diff --git a/library/Icingadb/Web/Control/ProblemToggle.php b/library/Icingadb/Web/Control/ProblemToggle.php
index 9c564d68..c5aed82d 100644
--- a/library/Icingadb/Web/Control/ProblemToggle.php
+++ b/library/Icingadb/Web/Control/ProblemToggle.php
@@ -32,7 +32,7 @@ class ProblemToggle extends CompatForm
      *
      * @return  $this
      */
-    public function setIdProtector($protector)
+    public function setIdProtector(callable $protector): self
     {
         $this->protector = $protector;
 
@@ -44,7 +44,7 @@ class ProblemToggle extends CompatForm
      *
      * @return bool
      */
-    public function isChecked()
+    public function isChecked(): bool
     {
         $this->ensureAssembled();
 
diff --git a/library/Icingadb/Web/Control/SearchBar/ObjectSuggestions.php b/library/Icingadb/Web/Control/SearchBar/ObjectSuggestions.php
index 22be30dd..741c04c7 100644
--- a/library/Icingadb/Web/Control/SearchBar/ObjectSuggestions.php
+++ b/library/Icingadb/Web/Control/SearchBar/ObjectSuggestions.php
@@ -4,6 +4,7 @@
 
 namespace Icinga\Module\Icingadb\Web\Control\SearchBar;
 
+use Generator;
 use Icinga\Module\Icingadb\Common\Auth;
 use Icinga\Module\Icingadb\Common\Database;
 use Icinga\Module\Icingadb\Model\Behavior\ReRoute;
@@ -61,7 +62,7 @@ class ObjectSuggestions extends Suggestions
      *
      * @return $this
      */
-    public function setModel($model)
+    public function setModel($model): self
     {
         if (is_string($model)) {
             $model = new $model();
@@ -77,8 +78,14 @@ class ObjectSuggestions extends Suggestions
      *
      * @return Model
      */
-    public function getModel()
+    public function getModel(): Model
     {
+        if ($this->model === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->model;
     }
 
@@ -216,7 +223,7 @@ class ObjectSuggestions extends Suggestions
      *
      * @return Select
      */
-    protected function queryCustomvarConfig($searchTerm)
+    protected function queryCustomvarConfig(string $searchTerm): Select
     {
         $customVars = CustomvarFlat::on($this->getDb());
         $tableName = $customVars->getModel()->getTableName();
@@ -260,9 +267,9 @@ class ObjectSuggestions extends Suggestions
      * @param Model $model
      * @param Resolver $resolver
      *
-     * @return \Generator
+     * @return Generator
      */
-    public static function collectFilterColumns(Model $model, Resolver $resolver = null)
+    public static function collectFilterColumns(Model $model, Resolver $resolver = null): Generator
     {
         if ($resolver === null) {
             $resolver = new Resolver();
diff --git a/library/Icingadb/Web/Control/ViewModeSwitcher.php b/library/Icingadb/Web/Control/ViewModeSwitcher.php
index 54b4ad06..1ff30a7a 100644
--- a/library/Icingadb/Web/Control/ViewModeSwitcher.php
+++ b/library/Icingadb/Web/Control/ViewModeSwitcher.php
@@ -51,7 +51,7 @@ class ViewModeSwitcher extends Form
      *
      * @return string
      */
-    public function getDefaultViewMode()
+    public function getDefaultViewMode(): string
     {
         return $this->defaultViewMode ?: static::DEFAULT_VIEW_MODE;
     }
@@ -63,7 +63,7 @@ class ViewModeSwitcher extends Form
      *
      * @return $this
      */
-    public function setDefaultViewMode($defaultViewMode)
+    public function setDefaultViewMode(string $defaultViewMode): self
     {
         $this->defaultViewMode = $defaultViewMode;
 
@@ -75,7 +75,7 @@ class ViewModeSwitcher extends Form
      *
      * @return string
      */
-    public function getViewModeParam()
+    public function getViewModeParam(): string
     {
         return $this->viewModeParam;
     }
@@ -87,7 +87,7 @@ class ViewModeSwitcher extends Form
      *
      * @return $this
      */
-    public function setViewModeParam($viewModeParam)
+    public function setViewModeParam(string $viewModeParam): self
     {
         $this->viewModeParam = $viewModeParam;
 
@@ -99,7 +99,7 @@ class ViewModeSwitcher extends Form
      *
      * @return string
      */
-    public function getViewMode()
+    public function getViewMode(): string
     {
         return $this->getValue($this->getViewModeParam(), $this->getDefaultViewMode());
     }
@@ -111,7 +111,7 @@ class ViewModeSwitcher extends Form
      *
      * @return  $this
      */
-    public function setIdProtector($protector)
+    public function setIdProtector(callable $protector): self
     {
         $this->protector = $protector;
 
diff --git a/library/Icingadb/Web/Controller.php b/library/Icingadb/Web/Controller.php
index aee01874..26fa950c 100644
--- a/library/Icingadb/Web/Controller.php
+++ b/library/Icingadb/Web/Controller.php
@@ -50,7 +50,7 @@ class Controller extends CompatController
     use Auth;
     use Database;
 
-    /** @var Filter Filter from query string parameters */
+    /** @var Filter\Rule Filter from query string parameters */
     private $filter;
 
     /** @var string|null */
@@ -64,7 +64,7 @@ class Controller extends CompatController
      *
      * @return Filter\Rule
      */
-    public function getFilter()
+    public function getFilter(): Filter\Rule
     {
         if ($this->filter === null) {
             $this->filter = QueryString::parse((string) $this->params);
@@ -80,7 +80,7 @@ class Controller extends CompatController
      *
      * @return LimitControl
      */
-    public function createLimitControl()
+    public function createLimitControl(): LimitControl
     {
         $limitControl = new LimitControl(Url::fromRequest());
         $limitControl->setDefaultLimit($this->getPageSize(null));
@@ -97,7 +97,7 @@ class Controller extends CompatController
      *
      * @return PaginationControl
      */
-    public function createPaginationControl(Paginatable $paginatable)
+    public function createPaginationControl(Paginatable $paginatable): PaginationControl
     {
         $paginationControl = new PaginationControl($paginatable, Url::fromRequest());
         $paginationControl->setDefaultPageSize($this->getPageSize(null));
@@ -119,7 +119,7 @@ class Controller extends CompatController
      *
      * @return SortControl
      */
-    public function createSortControl(Query $query, array $columns)
+    public function createSortControl(Query $query, array $columns): SortControl
     {
         $default = (array) $query->getModel()->getDefaultSort();
         $normalized = [];
@@ -152,7 +152,7 @@ class Controller extends CompatController
      *
      * @return SearchBar
      */
-    public function createSearchBar(Query $query, array $preserveParams = null)
+    public function createSearchBar(Query $query, array $preserveParams = null): SearchBar
     {
         $requestUrl = Url::fromRequest();
         $redirectUrl = $preserveParams !== null
@@ -253,7 +253,7 @@ class Controller extends CompatController
      *
      * @return SearchEditor
      */
-    public function createSearchEditor(Query $query, array $preserveParams = null)
+    public function createSearchEditor(Query $query, array $preserveParams = null): SearchEditor
     {
         $requestUrl = Url::fromRequest();
         $redirectUrl = Url::fromPath('icingadb/' . $this->getRequest()->getControllerName());
@@ -333,7 +333,7 @@ class Controller extends CompatController
      *
      * @return ContinueWith
      */
-    public function createContinueWith(Url $detailsUrl, SearchBar $searchBar)
+    public function createContinueWith(Url $detailsUrl, SearchBar $searchBar): ContinueWith
     {
         $continueWith = new ContinueWith($detailsUrl, [$searchBar, 'getFilter']);
         $continueWith->setTitle(t('Show bulk processing actions for all filtered results'));
@@ -353,14 +353,15 @@ class Controller extends CompatController
      *
      * @param PaginationControl $paginationControl
      * @param LimitControl      $limitControl
+     * @param bool              $verticalPagination
      *
      * @return ViewModeSwitcher
      */
     public function createViewModeSwitcher(
         PaginationControl $paginationControl,
         LimitControl $limitControl,
-        $verticalPagination = false
-    ) {
+        bool $verticalPagination = false
+    ): ViewModeSwitcher {
         $viewModeSwitcher = new ViewModeSwitcher();
         $viewModeSwitcher->setIdProtector([$this->getRequest(), 'protectId']);
 
@@ -488,6 +489,8 @@ class Controller extends CompatController
      * Process a search request
      *
      * @param Query $query
+     *
+     * @return void
      */
     public function handleSearchRequest(Query $query)
     {
@@ -519,7 +522,7 @@ class Controller extends CompatController
      *
      * @throws SecurityException
      */
-    public function assertRouteAccess($name = null)
+    public function assertRouteAccess(string $name = null)
     {
         if (! $name) {
             $name = $this->getRequest()->getControllerName();
@@ -786,7 +789,7 @@ class Controller extends CompatController
         return parent::addContent($content);
     }
 
-    public function filter(Query $query, Filter\Rule $filter = null)
+    public function filter(Query $query, Filter\Rule $filter = null): self
     {
         if ($this->format !== 'sql' || $this->hasPermission('config/authentication/roles/show')) {
             $this->applyRestrictions($query);
diff --git a/library/Icingadb/Web/Navigation/Action.php b/library/Icingadb/Web/Navigation/Action.php
index 2922550c..b23bdbf6 100644
--- a/library/Icingadb/Web/Navigation/Action.php
+++ b/library/Icingadb/Web/Navigation/Action.php
@@ -85,7 +85,7 @@ class Action extends NavigationItem
     /**
      * Get the filter to use when being asked whether to render this action
      *
-     * @return  string
+     * @return  ?string
      */
     public function getFilter()
     {
diff --git a/library/Icingadb/Web/Navigation/Renderer/HostProblemsBadge.php b/library/Icingadb/Web/Navigation/Renderer/HostProblemsBadge.php
index be062c60..07a77c88 100644
--- a/library/Icingadb/Web/Navigation/Renderer/HostProblemsBadge.php
+++ b/library/Icingadb/Web/Navigation/Renderer/HostProblemsBadge.php
@@ -7,6 +7,7 @@ namespace Icinga\Module\Icingadb\Web\Navigation\Renderer;
 use Icinga\Module\Icingadb\Common\Auth;
 use Icinga\Module\Icingadb\Common\Links;
 use Icinga\Module\Icingadb\Model\HoststateSummary;
+use ipl\Web\Url;
 
 class HostProblemsBadge extends ProblemsBadge
 {
@@ -20,7 +21,7 @@ class HostProblemsBadge extends ProblemsBadge
         return $summary->first()->hosts_down_unhandled;
     }
 
-    protected function getUrl()
+    protected function getUrl(): Url
     {
         return Links::hosts()->setParams(['host.state.is_problem' => 'y', 'sort' => 'host.state.severity desc']);
     }
diff --git a/library/Icingadb/Web/Navigation/Renderer/ProblemsBadge.php b/library/Icingadb/Web/Navigation/Renderer/ProblemsBadge.php
index 228adf26..b7386c03 100644
--- a/library/Icingadb/Web/Navigation/Renderer/ProblemsBadge.php
+++ b/library/Icingadb/Web/Navigation/Renderer/ProblemsBadge.php
@@ -67,7 +67,7 @@ abstract class ProblemsBadge extends NavigationItemRenderer
      *
      * @return $this
      */
-    public function setState($state)
+    public function setState(string $state): self
     {
         $this->state = $state;
 
@@ -79,8 +79,14 @@ abstract class ProblemsBadge extends NavigationItemRenderer
      *
      * @return string
      */
-    public function getState()
+    public function getState(): string
     {
+        if ($this->state === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->state;
     }
 
@@ -91,7 +97,7 @@ abstract class ProblemsBadge extends NavigationItemRenderer
      *
      * @return $this
      */
-    public function setTitle($title)
+    public function setTitle(string $title): self
     {
         $this->title = $title;
 
@@ -103,12 +109,18 @@ abstract class ProblemsBadge extends NavigationItemRenderer
      *
      * @return string
      */
-    public function getTitle()
+    public function getTitle(): string
     {
+        if ($this->title === null) {
+            throw new \LogicException(
+                'You are accessing an unset property. Please make sure to set it beforehand.'
+            );
+        }
+
         return $this->title;
     }
 
-    public function render(NavigationItem $item = null)
+    public function render(NavigationItem $item = null): string
     {
         if ($item === null) {
             $item = $this->getItem();
diff --git a/library/Icingadb/Web/Navigation/Renderer/ServiceProblemsBadge.php b/library/Icingadb/Web/Navigation/Renderer/ServiceProblemsBadge.php
index 8006e2e0..3460885e 100644
--- a/library/Icingadb/Web/Navigation/Renderer/ServiceProblemsBadge.php
+++ b/library/Icingadb/Web/Navigation/Renderer/ServiceProblemsBadge.php
@@ -7,6 +7,7 @@ namespace Icinga\Module\Icingadb\Web\Navigation\Renderer;
 use Icinga\Module\Icingadb\Common\Auth;
 use Icinga\Module\Icingadb\Common\Links;
 use Icinga\Module\Icingadb\Model\ServicestateSummary;
+use ipl\Web\Url;
 
 class ServiceProblemsBadge extends ProblemsBadge
 {
@@ -20,7 +21,7 @@ class ServiceProblemsBadge extends ProblemsBadge
         return $summary->first()->services_critical_unhandled;
     }
 
-    protected function getUrl()
+    protected function getUrl(): Url
     {
         return Links::services()
             ->setParams(['service.state.is_problem' => 'y', 'sort' => 'service.state.severity desc']);
diff --git a/library/Icingadb/Widget/AttemptBall.php b/library/Icingadb/Widget/AttemptBall.php
index fce7ac97..e57c59c7 100644
--- a/library/Icingadb/Widget/AttemptBall.php
+++ b/library/Icingadb/Widget/AttemptBall.php
@@ -20,7 +20,7 @@ class AttemptBall extends BaseHtmlElement
      *
      * @param bool $taken Whether the attempt was taken
      */
-    public function __construct($taken = false)
+    public function __construct(bool $taken = false)
     {
         if ($taken) {
             $this->addAttributes(['class' => 'ball-size-s taken']);
diff --git a/library/Icingadb/Widget/CheckAttempt.php b/library/Icingadb/Widget/CheckAttempt.php
index 80fddd9b..cf12de34 100644
--- a/library/Icingadb/Widget/CheckAttempt.php
+++ b/library/Icingadb/Widget/CheckAttempt.php
@@ -28,7 +28,7 @@ class CheckAttempt extends BaseHtmlElement
      * @param int $attempt     Current check attempt
      * @param int $maxAttempts Max check attempts
      */
-    public function __construct($attempt, $maxAttempts)
+    public function __construct(int $attempt, int $maxAttempts)
     {
         $this->attempt = $attempt;
         $this->maxAttempts = $maxAttempts;
diff --git a/library/Icingadb/Widget/Detail/CommentDetail.php b/library/Icingadb/Widget/Detail/CommentDetail.php
index e406b7cc..3ca19e62 100644
--- a/library/Icingadb/Widget/Detail/CommentDetail.php
+++ b/library/Icingadb/Widget/Detail/CommentDetail.php
@@ -6,6 +6,7 @@ namespace Icinga\Module\Icingadb\Widget\Detail;
 
 use Icinga\Module\Icingadb\Common\Auth;
 use Icinga\Module\Icingadb\Common\Links;
+use Icinga\Module\Icingadb\Model\Comment;
 use Icinga\Module\Icingadb\Widget\MarkdownText;
 use Icinga\Module\Icingadb\Forms\Command\Object\DeleteCommentForm;
 use ipl\Web\Widget\TimeUntil;
@@ -22,12 +23,12 @@ class CommentDetail extends BaseHtmlElement
 
     protected $tag = 'div';
 
-    public function __construct($comment)
+    public function __construct(Comment $comment)
     {
         $this->comment = $comment;
     }
 
-    protected function createComment()
+    protected function createComment(): array
     {
         return [
             Html::tag('h2', t('Comment')),
@@ -35,7 +36,7 @@ class CommentDetail extends BaseHtmlElement
         ];
     }
 
-    protected function createDetails()
+    protected function createDetails(): array
     {
         $details = [];
 
diff --git a/library/Icingadb/Widget/Detail/DowntimeDetail.php b/library/Icingadb/Widget/Detail/DowntimeDetail.php
index b22d909c..f751e806 100644
--- a/library/Icingadb/Widget/Detail/DowntimeDetail.php
+++ b/library/Icingadb/Widget/Detail/DowntimeDetail.php
@@ -57,7 +57,7 @@ class DowntimeDetail extends BaseHtmlElement
 
     protected $tag = 'div';
 
-    public function __construct($downtime)
+    public function __construct(Downtime $downtime)
     {
         $this->downtime = $downtime;
 
@@ -90,7 +90,7 @@ class DowntimeDetail extends BaseHtmlElement
             ->setAction($action->getAbsoluteUrl());
     }
 
-    protected function createTimeline()
+    protected function createTimeline(): DowntimeCard
     {
         return new DowntimeCard($this->downtime);
     }
diff --git a/library/Icingadb/Widget/Detail/HostDetail.php b/library/Icingadb/Widget/Detail/HostDetail.php
index 1404afe9..b412069b 100644
--- a/library/Icingadb/Widget/Detail/HostDetail.php
+++ b/library/Icingadb/Widget/Detail/HostDetail.php
@@ -5,6 +5,7 @@
 namespace Icinga\Module\Icingadb\Widget\Detail;
 
 use Icinga\Module\Icingadb\Hook\ExtensionHook\ObjectDetailExtensionHook;
+use Icinga\Module\Icingadb\Model\ServicestateSummary;
 use Icinga\Module\Icingadb\Widget\EmptyState;
 use ipl\Html\Html;
 use ipl\Stdlib\Filter;
@@ -13,14 +14,14 @@ class HostDetail extends ObjectDetail
 {
     protected $serviceSummary;
 
-    public function __construct($object, $serviceSummary)
+    public function __construct($object, ServicestateSummary $serviceSummary)
     {
         parent::__construct($object);
 
         $this->serviceSummary = $serviceSummary;
     }
 
-    protected function createServiceStatistics()
+    protected function createServiceStatistics(): array
     {
         if ($this->serviceSummary->services_total > 0) {
             $services = new ServiceStatistics($this->serviceSummary);
diff --git a/library/Icingadb/Widget/Detail/HostStatistics.php b/library/Icingadb/Widget/Detail/HostStatistics.php
index d46bca15..53423bef 100644
--- a/library/Icingadb/Widget/Detail/HostStatistics.php
+++ b/library/Icingadb/Widget/Detail/HostStatistics.php
@@ -8,6 +8,7 @@ use Icinga\Chart\Donut;
 use Icinga\Data\Filter\Filter;
 use Icinga\Module\Icingadb\Common\Links;
 use Icinga\Module\Icingadb\Widget\HostStateBadges;
+use ipl\Html\ValidHtml;
 use ipl\Web\Widget\VerticalKeyValue;
 use ipl\Html\HtmlString;
 use ipl\Web\Filter\QueryString;
@@ -22,7 +23,7 @@ class HostStatistics extends ObjectStatistics
         $this->summary = $summary;
     }
 
-    protected function createDonut()
+    protected function createDonut(): ValidHtml
     {
         $donut = (new Donut())
             ->addSlice($this->summary->hosts_up, ['class' => 'slice-state-ok'])
@@ -33,7 +34,7 @@ class HostStatistics extends ObjectStatistics
         return HtmlString::create($donut->render());
     }
 
-    protected function createTotal()
+    protected function createTotal(): ValidHtml
     {
         $url = Links::hosts();
         if ($this->hasBaseFilter()) {
@@ -49,7 +50,7 @@ class HostStatistics extends ObjectStatistics
         );
     }
 
-    protected function createBadges()
+    protected function createBadges(): ValidHtml
     {
         $badges = new HostStateBadges($this->summary);
         if ($this->hasBaseFilter()) {
diff --git a/library/Icingadb/Widget/Detail/MultiselectQuickActions.php b/library/Icingadb/Widget/Detail/MultiselectQuickActions.php
index 692f33ed..b945cc00 100644
--- a/library/Icingadb/Widget/Detail/MultiselectQuickActions.php
+++ b/library/Icingadb/Widget/Detail/MultiselectQuickActions.php
@@ -165,7 +165,7 @@ class MultiselectQuickActions extends BaseHtmlElement
         }
     }
 
-    protected function assembleAction($action, $label, $icon, $title)
+    protected function assembleAction(string $action, string $label, string $icon, string $title)
     {
         $link = Html::tag(
             'a',
@@ -185,7 +185,7 @@ class MultiselectQuickActions extends BaseHtmlElement
         $this->add(Html::tag('li', $link));
     }
 
-    protected function getLink($action)
+    protected function getLink(string $action): string
     {
         return Url::fromPath("icingadb/{$this->type}s/$action")
             ->setQueryString(QueryString::render($this->getBaseFilter()))
diff --git a/library/Icingadb/Widget/Detail/ObjectDetail.php b/library/Icingadb/Widget/Detail/ObjectDetail.php
index 34a3511e..8ec5d879 100644
--- a/library/Icingadb/Widget/Detail/ObjectDetail.php
+++ b/library/Icingadb/Widget/Detail/ObjectDetail.php
@@ -138,7 +138,7 @@ class ObjectDetail extends BaseHtmlElement
         ];
     }
 
-    protected function createCheckStatistics()
+    protected function createCheckStatistics(): array
     {
         return [
             Html::tag('h2', t('Check Statistics')),
@@ -146,7 +146,7 @@ class ObjectDetail extends BaseHtmlElement
         ];
     }
 
-    protected function createComments()
+    protected function createComments(): array
     {
         if ($this->objectType === 'host') {
             $link = HostLinks::comments($this->object);
@@ -178,7 +178,7 @@ class ObjectDetail extends BaseHtmlElement
         return $content;
     }
 
-    protected function createCustomVars()
+    protected function createCustomVars(): array
     {
         $content = [Html::tag('h2', t('Custom Variables'))];
 
@@ -195,7 +195,7 @@ class ObjectDetail extends BaseHtmlElement
         return $content;
     }
 
-    protected function createDowntimes()
+    protected function createDowntimes(): array
     {
         if ($this->objectType === 'host') {
             $link = HostLinks::downtimes($this->object);
@@ -227,7 +227,7 @@ class ObjectDetail extends BaseHtmlElement
         return $content;
     }
 
-    protected function createGroups()
+    protected function createGroups(): array
     {
         $groups = [Html::tag('h2', t('Groups'))];
 
@@ -314,7 +314,7 @@ class ObjectDetail extends BaseHtmlElement
         return $content;
     }
 
-    protected function createNotifications()
+    protected function createNotifications(): array
     {
         list($users, $usergroups) = $this->getUsersAndUsergroups();
 
@@ -347,7 +347,7 @@ class ObjectDetail extends BaseHtmlElement
         ];
     }
 
-    protected function createPerformanceData()
+    protected function createPerformanceData(): array
     {
         $content[] = Html::tag('h2', t('Performance Data'));
 
@@ -364,7 +364,7 @@ class ObjectDetail extends BaseHtmlElement
         return $content;
     }
 
-    protected function createPluginOutput()
+    protected function createPluginOutput(): array
     {
         if (empty($this->object->state->output) && empty($this->object->state->long_output)) {
             $pluginOutput = new EmptyState(t('Output unavailable.'));
@@ -386,7 +386,7 @@ class ObjectDetail extends BaseHtmlElement
         ];
     }
 
-    protected function createExtensions()
+    protected function createExtensions(): array
     {
         $extensions = ObjectDetailExtensionHook::loadExtensions($this->object);
 
@@ -457,7 +457,7 @@ class ObjectDetail extends BaseHtmlElement
         return $extensions;
     }
 
-    protected function createFeatureToggles()
+    protected function createFeatureToggles(): array
     {
         $form = new ToggleObjectFeaturesForm($this->object);
 
@@ -473,7 +473,7 @@ class ObjectDetail extends BaseHtmlElement
         ];
     }
 
-    protected function getUsersAndUsergroups()
+    protected function getUsersAndUsergroups(): array
     {
         $users = [];
         $usergroups = [];
diff --git a/library/Icingadb/Widget/Detail/ObjectStatistics.php b/library/Icingadb/Widget/Detail/ObjectStatistics.php
index 34eb8e1b..2142c8b6 100644
--- a/library/Icingadb/Widget/Detail/ObjectStatistics.php
+++ b/library/Icingadb/Widget/Detail/ObjectStatistics.php
@@ -7,6 +7,7 @@ namespace Icinga\Module\Icingadb\Widget\Detail;
 use Icinga\Module\Icingadb\Common\BaseFilter;
 use ipl\Html\BaseHtmlElement;
 use ipl\Html\Html;
+use ipl\Html\ValidHtml;
 
 abstract class ObjectStatistics extends BaseHtmlElement
 {
@@ -16,11 +17,11 @@ abstract class ObjectStatistics extends BaseHtmlElement
 
     protected $defaultAttributes = ['class' => 'object-statistics'];
 
-    abstract protected function createDonut();
+    abstract protected function createDonut(): ValidHtml;
 
-    abstract protected function createTotal();
+    abstract protected function createTotal(): ValidHtml;
 
-    abstract protected function createBadges();
+    abstract protected function createBadges(): ValidHtml;
 
     protected function assemble()
     {
diff --git a/library/Icingadb/Widget/Detail/ObjectsDetail.php b/library/Icingadb/Widget/Detail/ObjectsDetail.php
index f978a1e0..18b55667 100644
--- a/library/Icingadb/Widget/Detail/ObjectsDetail.php
+++ b/library/Icingadb/Widget/Detail/ObjectsDetail.php
@@ -9,10 +9,14 @@ use Icinga\Module\Icingadb\Common\BaseFilter;
 use Icinga\Module\Icingadb\Common\Links;
 use Icinga\Module\Icingadb\Forms\Command\Object\ToggleObjectFeaturesForm;
 use Icinga\Module\Icingadb\Hook\ExtensionHook\ObjectsDetailExtensionHook;
+use Icinga\Module\Icingadb\Model\HoststateSummary;
+use Icinga\Module\Icingadb\Model\ServicestateSummary;
 use Icinga\Module\Icingadb\Util\FeatureStatus;
 use Icinga\Module\Icingadb\Widget\EmptyState;
 use Icinga\Module\Icingadb\Widget\HostStateBadges;
 use Icinga\Module\Icingadb\Widget\ServiceStateBadges;
+use ipl\Html\HtmlElement;
+use ipl\Orm\Query;
 use ipl\Web\Widget\VerticalKeyValue;
 use ipl\Html\BaseHtmlElement;
 use ipl\Html\Html;
@@ -34,14 +38,21 @@ class ObjectsDetail extends BaseHtmlElement
 
     protected $tag = 'div';
 
-    public function __construct($type, $summary, $query)
+    /**
+     * Construct an object detail summary widget
+     *
+     * @param string $type
+     * @param HoststateSummary|ServicestateSummary $summary
+     * @param Query $query
+     */
+    public function __construct(string $type, $summary, Query $query)
     {
         $this->summary = $summary;
         $this->query = $query;
         $this->type = $type;
     }
 
-    protected function createChart()
+    protected function createChart(): BaseHtmlElement
     {
         $content = Html::tag('div', ['class' => 'multiselect-summary']);
 
@@ -90,7 +101,7 @@ class ObjectsDetail extends BaseHtmlElement
         return $content;
     }
 
-    protected function createComments()
+    protected function createComments(): array
     {
         $content = [Html::tag('h2', t('Comments'))];
 
@@ -109,7 +120,7 @@ class ObjectsDetail extends BaseHtmlElement
         return $content;
     }
 
-    protected function createDowntimes()
+    protected function createDowntimes(): array
     {
         $content = [Html::tag('h2', t('Downtimes'))];
 
@@ -128,7 +139,7 @@ class ObjectsDetail extends BaseHtmlElement
         return $content;
     }
 
-    protected function createFeatureToggles()
+    protected function createFeatureToggles(): array
     {
         $form = new ToggleObjectFeaturesForm(new FeatureStatus($this->type, $this->summary));
 
@@ -152,7 +163,7 @@ class ObjectsDetail extends BaseHtmlElement
         ];
     }
 
-    protected function createExtensions()
+    protected function createExtensions(): array
     {
         return ObjectsDetailExtensionHook::loadExtensions(
             $this->type,
@@ -161,7 +172,7 @@ class ObjectsDetail extends BaseHtmlElement
         );
     }
 
-    protected function createSummary()
+    protected function createSummary(): array
     {
         return [
             Html::tag('h2', t('Summary')),
diff --git a/library/Icingadb/Widget/Detail/PerfDataTable.php b/library/Icingadb/Widget/Detail/PerfDataTable.php
index a554fb53..639fb6b9 100644
--- a/library/Icingadb/Widget/Detail/PerfDataTable.php
+++ b/library/Icingadb/Widget/Detail/PerfDataTable.php
@@ -38,10 +38,8 @@ class PerfDataTable extends Table
      * @param   string  $perfdataStr    The perfdata string
      * @param   int       $limit              Max labels to show; 0 for no limit
      * @param   string  $color             The color indicating the perfdata state
-     *
-     * @return string
      */
-    public function __construct($perfdataStr, $limit = 0, $color = PerfData::PERFDATA_OK)
+    public function __construct(string $perfdataStr, int $limit = 0, string $color = PerfData::PERFDATA_OK)
     {
         $this->perfdataStr = $perfdataStr;
         $this->limit = $limit;
diff --git a/library/Icingadb/Widget/Detail/QuickActions.php b/library/Icingadb/Widget/Detail/QuickActions.php
index 088675ba..6ce90cd6 100644
--- a/library/Icingadb/Widget/Detail/QuickActions.php
+++ b/library/Icingadb/Widget/Detail/QuickActions.php
@@ -117,7 +117,7 @@ class QuickActions extends BaseHtmlElement
         }
     }
 
-    protected function assembleAction($action, $label, $icon, $title)
+    protected function assembleAction(string $action, string $label, string $icon, string $title)
     {
         $link = Html::tag(
             'a',
diff --git a/library/Icingadb/Widget/Detail/ServiceStatistics.php b/library/Icingadb/Widget/Detail/ServiceStatistics.php
index 989ae9f9..0f570b44 100644
--- a/library/Icingadb/Widget/Detail/ServiceStatistics.php
+++ b/library/Icingadb/Widget/Detail/ServiceStatistics.php
@@ -8,6 +8,7 @@ use Icinga\Chart\Donut;
 use Icinga\Data\Filter\Filter;
 use Icinga\Module\Icingadb\Common\Links;
 use Icinga\Module\Icingadb\Widget\ServiceStateBadges;
+use ipl\Html\ValidHtml;
 use ipl\Web\Widget\VerticalKeyValue;
 use ipl\Html\HtmlString;
 use ipl\Web\Filter\QueryString;
@@ -22,7 +23,7 @@ class ServiceStatistics extends ObjectStatistics
         $this->summary = $summary;
     }
 
-    protected function createDonut()
+    protected function createDonut(): ValidHtml
     {
         $donut = (new Donut())
             ->addSlice($this->summary->services_ok, ['class' => 'slice-state-ok'])
@@ -37,7 +38,7 @@ class ServiceStatistics extends ObjectStatistics
         return HtmlString::create($donut->render());
     }
 
-    protected function createTotal()
+    protected function createTotal(): ValidHtml
     {
         $url = Links::services();
         if ($this->hasBaseFilter()) {
@@ -53,7 +54,7 @@ class ServiceStatistics extends ObjectStatistics
         );
     }
 
-    protected function createBadges()
+    protected function createBadges(): ValidHtml
     {
         $badges = new ServiceStateBadges($this->summary);
         if ($this->hasBaseFilter()) {
diff --git a/library/Icingadb/Widget/Detail/UserDetail.php b/library/Icingadb/Widget/Detail/UserDetail.php
index 4753552c..5ae79617 100644
--- a/library/Icingadb/Widget/Detail/UserDetail.php
+++ b/library/Icingadb/Widget/Detail/UserDetail.php
@@ -34,7 +34,7 @@ class UserDetail extends BaseHtmlElement
         $this->user = $user;
     }
 
-    protected function createCustomVars()
+    protected function createCustomVars(): array
     {
         $content = [new HtmlElement('h2', null, Text::create(t('Custom Variables')))];
         $flattenedVars = $this->user->customvar_flat;
@@ -52,7 +52,7 @@ class UserDetail extends BaseHtmlElement
         return $content;
     }
 
-    protected function createUserDetail()
+    protected function createUserDetail(): array
     {
         list($hostStates, $serviceStates) = $this->separateStates($this->user->states);
         $hostStates = implode(', ', $this->localizeStates($hostStates));
@@ -69,7 +69,7 @@ class UserDetail extends BaseHtmlElement
         ];
     }
 
-    protected function createUsergroupList()
+    protected function createUsergroupList(): array
     {
         $userGroups = $this->user->usergroup->limit(6)->peekAhead()->execute();
 
@@ -85,7 +85,7 @@ class UserDetail extends BaseHtmlElement
         ];
     }
 
-    protected function createExtensions()
+    protected function createExtensions(): array
     {
         return ObjectDetailExtensionHook::loadExtensions($this->user);
     }
@@ -99,7 +99,7 @@ class UserDetail extends BaseHtmlElement
         ], $this->createExtensions()));
     }
 
-    private function localizeTypes(array $types)
+    private function localizeTypes(array $types): array
     {
         $localizedTypes = [];
         foreach ($types as $type) {
@@ -137,7 +137,7 @@ class UserDetail extends BaseHtmlElement
         return $localizedTypes;
     }
 
-    private function localizeStates(array $states)
+    private function localizeStates(array $states): array
     {
         $localizedState = [];
         foreach ($states as $state) {
@@ -166,7 +166,7 @@ class UserDetail extends BaseHtmlElement
         return $localizedState;
     }
 
-    private function separateStates(array $states)
+    private function separateStates(array $states): array
     {
         $hostStates = [];
         $serviceStates = [];
diff --git a/library/Icingadb/Widget/Detail/UsergroupDetail.php b/library/Icingadb/Widget/Detail/UsergroupDetail.php
index 00434517..fd6a2f50 100644
--- a/library/Icingadb/Widget/Detail/UsergroupDetail.php
+++ b/library/Icingadb/Widget/Detail/UsergroupDetail.php
@@ -33,7 +33,7 @@ class UsergroupDetail extends BaseHtmlElement
         $this->usergroup = $usergroup;
     }
 
-    protected function createCustomVars()
+    protected function createCustomVars(): array
     {
         $content = [new HtmlElement('h2', null, Text::create(t('Custom Variables')))];
         $flattenedVars = $this->usergroup->customvar_flat;
@@ -51,7 +51,7 @@ class UsergroupDetail extends BaseHtmlElement
         return $content;
     }
 
-    protected function createUserList()
+    protected function createUserList(): array
     {
         $users = $this->usergroup->user->limit(6)->peekAhead()->execute();
 
@@ -67,7 +67,7 @@ class UsergroupDetail extends BaseHtmlElement
         ];
     }
 
-    protected function createExtensions()
+    protected function createExtensions(): array
     {
         return ObjectDetailExtensionHook::loadExtensions($this->usergroup);
     }
diff --git a/library/Icingadb/Widget/HostStateBadges.php b/library/Icingadb/Widget/HostStateBadges.php
index 30024053..85b19486 100644
--- a/library/Icingadb/Widget/HostStateBadges.php
+++ b/library/Icingadb/Widget/HostStateBadges.php
@@ -7,20 +7,21 @@ namespace Icinga\Module\Icingadb\Widget;
 use Icinga\Module\Icingadb\Common\HostStates;
 use Icinga\Module\Icingadb\Common\Links;
 use Icinga\Module\Icingadb\Common\StateBadges;
+use ipl\Web\Url;
 
 class HostStateBadges extends StateBadges
 {
-    protected function getBaseUrl()
+    protected function getBaseUrl(): Url
     {
         return Links::hosts();
     }
 
-    protected function getPrefix()
+    protected function getPrefix(): string
     {
         return 'hosts';
     }
 
-    protected function getStateInt($state)
+    protected function getStateInt(string $state): int
     {
         return HostStates::int($state);
     }
diff --git a/library/Icingadb/Widget/HostStatusBar.php b/library/Icingadb/Widget/HostStatusBar.php
index 7690ee02..0014b5ec 100644
--- a/library/Icingadb/Widget/HostStatusBar.php
+++ b/library/Icingadb/Widget/HostStatusBar.php
@@ -14,7 +14,7 @@ class HostStatusBar extends BaseStatusBar
         $total->add(sprintf(tp('%d Host', '%d Hosts', $this->summary->hosts_total), $this->summary->hosts_total));
     }
 
-    protected function createStateBadges()
+    protected function createStateBadges(): BaseHtmlElement
     {
         return new HostStateBadges($this->summary);
     }
diff --git a/library/Icingadb/Widget/ItemList/BaseDowntimeListItem.php b/library/Icingadb/Widget/ItemList/BaseDowntimeListItem.php
index a65160e5..445c3461 100644
--- a/library/Icingadb/Widget/ItemList/BaseDowntimeListItem.php
+++ b/library/Icingadb/Widget/ItemList/BaseDowntimeListItem.php
@@ -88,7 +88,7 @@ abstract class BaseDowntimeListItem extends BaseListItem
         }
     }
 
-    protected function createProgress()
+    protected function createProgress(): BaseHtmlElement
     {
         $ref = floor(
             (float) ($this->currentTime - $this->startTime)
diff --git a/library/Icingadb/Widget/ItemList/BaseHistoryListItem.php b/library/Icingadb/Widget/ItemList/BaseHistoryListItem.php
index 8a117c41..e6d96b2c 100644
--- a/library/Icingadb/Widget/ItemList/BaseHistoryListItem.php
+++ b/library/Icingadb/Widget/ItemList/BaseHistoryListItem.php
@@ -46,7 +46,7 @@ abstract class BaseHistoryListItem extends BaseListItem
         $this->list->addDetailFilterAttribute($this, Filter::equal('id', bin2hex($this->item->id)));
     }
 
-    abstract protected function getStateBallSize();
+    abstract protected function getStateBallSize(): string;
 
     protected function assembleCaption(BaseHtmlElement $caption)
     {
diff --git a/library/Icingadb/Widget/ItemList/BaseHostListItem.php b/library/Icingadb/Widget/ItemList/BaseHostListItem.php
index 7413c699..99a8c631 100644
--- a/library/Icingadb/Widget/ItemList/BaseHostListItem.php
+++ b/library/Icingadb/Widget/ItemList/BaseHostListItem.php
@@ -8,6 +8,7 @@ use Icinga\Module\Icingadb\Common\Links;
 use Icinga\Module\Icingadb\Common\NoSubjectLink;
 use Icinga\Module\Icingadb\Model\Host;
 use ipl\Html\Attributes;
+use ipl\Html\BaseHtmlElement;
 use ipl\Html\HtmlElement;
 use ipl\Html\Text;
 use ipl\Stdlib\Filter;
@@ -23,6 +24,11 @@ abstract class BaseHostListItem extends StateListItem
 {
     use NoSubjectLink;
 
+    /**
+     * Create new subject link
+     *
+     * @return BaseHtmlElement
+     */
     protected function createSubject()
     {
         if ($this->getNoSubjectLink()) {
diff --git a/library/Icingadb/Widget/ItemList/BaseNotificationListItem.php b/library/Icingadb/Widget/ItemList/BaseNotificationListItem.php
index 77723d12..dde6d1e3 100644
--- a/library/Icingadb/Widget/ItemList/BaseNotificationListItem.php
+++ b/library/Icingadb/Widget/ItemList/BaseNotificationListItem.php
@@ -46,7 +46,7 @@ abstract class BaseNotificationListItem extends BaseListItem
      *
      * @return string
      */
-    public static function phraseForType($type)
+    public static function phraseForType(string $type): string
     {
         switch ($type) {
             case 'acknowledgement':
diff --git a/library/Icingadb/Widget/ItemList/CommandTransportList.php b/library/Icingadb/Widget/ItemList/CommandTransportList.php
index 615e7d64..50ae06dc 100644
--- a/library/Icingadb/Widget/ItemList/CommandTransportList.php
+++ b/library/Icingadb/Widget/ItemList/CommandTransportList.php
@@ -15,7 +15,7 @@ class CommandTransportList extends BaseOrderedItemList
         $this->setDetailUrl(Url::fromPath('icingadb/command-transport/show'));
     }
 
-    protected function getItemClass()
+    protected function getItemClass(): string
     {
         return CommandTransportListItem::class;
     }
diff --git a/library/Icingadb/Widget/ItemList/CommentList.php b/library/Icingadb/Widget/ItemList/CommentList.php
index 7e2c54d3..84160c4b 100644
--- a/library/Icingadb/Widget/ItemList/CommentList.php
+++ b/library/Icingadb/Widget/ItemList/CommentList.php
@@ -21,7 +21,7 @@ class CommentList extends BaseItemList
 
     protected $defaultAttributes = ['class' => 'comment-list'];
 
-    protected function getItemClass()
+    protected function getItemClass(): string
     {
         $viewMode = $this->getViewMode();
 
diff --git a/library/Icingadb/Widget/ItemList/DowntimeList.php b/library/Icingadb/Widget/ItemList/DowntimeList.php
index ea2699e4..abb4e5cf 100644
--- a/library/Icingadb/Widget/ItemList/DowntimeList.php
+++ b/library/Icingadb/Widget/ItemList/DowntimeList.php
@@ -21,7 +21,7 @@ class DowntimeList extends BaseItemList
 
     protected $defaultAttributes = ['class' => 'downtime-list'];
 
-    protected function getItemClass()
+    protected function getItemClass(): string
     {
         $viewMode = $this->getViewMode();
 
diff --git a/library/Icingadb/Widget/ItemList/HistoryList.php b/library/Icingadb/Widget/ItemList/HistoryList.php
index 58b07ef2..7d69a10e 100644
--- a/library/Icingadb/Widget/ItemList/HistoryList.php
+++ b/library/Icingadb/Widget/ItemList/HistoryList.php
@@ -35,7 +35,7 @@ class HistoryList extends BaseItemList
         $this->setDetailUrl(Url::fromPath('icingadb/event'));
     }
 
-    protected function getItemClass()
+    protected function getItemClass(): string
     {
         switch ($this->getViewMode()) {
             case 'minimal':
diff --git a/library/Icingadb/Widget/ItemList/HistoryListItem.php b/library/Icingadb/Widget/ItemList/HistoryListItem.php
index d1d8a7e1..c44a8076 100644
--- a/library/Icingadb/Widget/ItemList/HistoryListItem.php
+++ b/library/Icingadb/Widget/ItemList/HistoryListItem.php
@@ -11,7 +11,7 @@ class HistoryListItem extends BaseHistoryListItem
 {
     use ListItemCommonLayout;
 
-    protected function getStateBallSize()
+    protected function getStateBallSize(): string
     {
         return StateBall::SIZE_LARGE;
     }
diff --git a/library/Icingadb/Widget/ItemList/HistoryListItemDetailed.php b/library/Icingadb/Widget/ItemList/HistoryListItemDetailed.php
index a1f542b1..7129d2da 100644
--- a/library/Icingadb/Widget/ItemList/HistoryListItemDetailed.php
+++ b/library/Icingadb/Widget/ItemList/HistoryListItemDetailed.php
@@ -11,7 +11,7 @@ class HistoryListItemDetailed extends BaseHistoryListItem
 {
     use ListItemDetailedLayout;
 
-    protected function getStateBallSize()
+    protected function getStateBallSize(): string
     {
         return StateBall::SIZE_LARGE;
     }
diff --git a/library/Icingadb/Widget/ItemList/HistoryListItemMinimal.php b/library/Icingadb/Widget/ItemList/HistoryListItemMinimal.php
index 4205566b..b516a4e3 100644
--- a/library/Icingadb/Widget/ItemList/HistoryListItemMinimal.php
+++ b/library/Icingadb/Widget/ItemList/HistoryListItemMinimal.php
@@ -20,7 +20,7 @@ class HistoryListItemMinimal extends BaseHistoryListItem
         }
     }
 
-    protected function getStateBallSize()
+    protected function getStateBallSize(): string
     {
         return StateBall::SIZE_BIG;
     }
diff --git a/library/Icingadb/Widget/ItemList/HostDetailHeader.php b/library/Icingadb/Widget/ItemList/HostDetailHeader.php
index 8e96bbaa..cc9552a5 100644
--- a/library/Icingadb/Widget/ItemList/HostDetailHeader.php
+++ b/library/Icingadb/Widget/ItemList/HostDetailHeader.php
@@ -12,7 +12,7 @@ use ipl\Web\Widget\StateBall;
 
 class HostDetailHeader extends HostListItemMinimal
 {
-    protected function getStateBallSize()
+    protected function getStateBallSize(): string
     {
         if ($this->state->state_type === 'soft') {
             return StateBall::SIZE_MEDIUM_LARGE;
diff --git a/library/Icingadb/Widget/ItemList/HostList.php b/library/Icingadb/Widget/ItemList/HostList.php
index 00e11f67..51d218e1 100644
--- a/library/Icingadb/Widget/ItemList/HostList.php
+++ b/library/Icingadb/Widget/ItemList/HostList.php
@@ -14,7 +14,7 @@ class HostList extends StateList
 {
     protected $defaultAttributes = ['class' => 'host-list'];
 
-    protected function getItemClass()
+    protected function getItemClass(): string
     {
         switch ($this->getViewMode()) {
             case 'minimal':
diff --git a/library/Icingadb/Widget/ItemList/HostListItem.php b/library/Icingadb/Widget/ItemList/HostListItem.php
index b1d0e71d..2eae6600 100644
--- a/library/Icingadb/Widget/ItemList/HostListItem.php
+++ b/library/Icingadb/Widget/ItemList/HostListItem.php
@@ -11,7 +11,7 @@ class HostListItem extends BaseHostListItem
 {
     use ListItemCommonLayout;
 
-    protected function getStateBallSize()
+    protected function getStateBallSize(): string
     {
         return StateBall::SIZE_LARGE;
     }
diff --git a/library/Icingadb/Widget/ItemList/HostListItemDetailed.php b/library/Icingadb/Widget/ItemList/HostListItemDetailed.php
index b1d51b11..48060b90 100644
--- a/library/Icingadb/Widget/ItemList/HostListItemDetailed.php
+++ b/library/Icingadb/Widget/ItemList/HostListItemDetailed.php
@@ -22,7 +22,7 @@ class HostListItemDetailed extends BaseHostListItem
     /** @var int Max pie charts to be shown */
     const PIE_CHART_LIMIT = 5;
 
-    protected function getStateBallSize()
+    protected function getStateBallSize(): string
     {
         return StateBall::SIZE_LARGE;
     }
diff --git a/library/Icingadb/Widget/ItemList/HostListItemMinimal.php b/library/Icingadb/Widget/ItemList/HostListItemMinimal.php
index 053d3a9e..f04b991e 100644
--- a/library/Icingadb/Widget/ItemList/HostListItemMinimal.php
+++ b/library/Icingadb/Widget/ItemList/HostListItemMinimal.php
@@ -11,7 +11,7 @@ class HostListItemMinimal extends BaseHostListItem
 {
     use ListItemMinimalLayout;
 
-    protected function getStateBallSize()
+    protected function getStateBallSize(): string
     {
         return StateBall::SIZE_BIG;
     }
diff --git a/library/Icingadb/Widget/ItemList/HostgroupList.php b/library/Icingadb/Widget/ItemList/HostgroupList.php
index 3c132aae..e6c8279d 100644
--- a/library/Icingadb/Widget/ItemList/HostgroupList.php
+++ b/library/Icingadb/Widget/ItemList/HostgroupList.php
@@ -24,7 +24,7 @@ class HostgroupList extends BaseItemList
         $this->setDetailUrl(Url::fromPath('icingadb/hostgroup'));
     }
 
-    protected function getItemClass()
+    protected function getItemClass(): string
     {
         $this->addAttributes(['class' => $this->getViewMode()]);
 
diff --git a/library/Icingadb/Widget/ItemList/NotificationList.php b/library/Icingadb/Widget/ItemList/NotificationList.php
index b0f53cc0..8c95d267 100644
--- a/library/Icingadb/Widget/ItemList/NotificationList.php
+++ b/library/Icingadb/Widget/ItemList/NotificationList.php
@@ -35,7 +35,7 @@ class NotificationList extends BaseItemList
         $this->setDetailUrl(Url::fromPath('icingadb/event'));
     }
 
-    protected function getItemClass()
+    protected function getItemClass(): string
     {
         switch ($this->getViewMode()) {
             case 'minimal':
diff --git a/library/Icingadb/Widget/ItemList/NotificationListItem.php b/library/Icingadb/Widget/ItemList/NotificationListItem.php
index f2a68e14..683762f9 100644
--- a/library/Icingadb/Widget/ItemList/NotificationListItem.php
+++ b/library/Icingadb/Widget/ItemList/NotificationListItem.php
@@ -11,7 +11,7 @@ class NotificationListItem extends BaseNotificationListItem
 {
     use ListItemCommonLayout;
 
-    protected function getStateBallSize()
+    protected function getStateBallSize(): string
     {
         return StateBall::SIZE_LARGE;
     }
diff --git a/library/Icingadb/Widget/ItemList/NotificationListItemDetailed.php b/library/Icingadb/Widget/ItemList/NotificationListItemDetailed.php
index 9901a4bd..0a7449ec 100644
--- a/library/Icingadb/Widget/ItemList/NotificationListItemDetailed.php
+++ b/library/Icingadb/Widget/ItemList/NotificationListItemDetailed.php
@@ -11,7 +11,7 @@ class NotificationListItemDetailed extends BaseNotificationListItem
 {
     use ListItemDetailedLayout;
 
-    protected function getStateBallSize()
+    protected function getStateBallSize(): string
     {
         return StateBall::SIZE_LARGE;
     }
diff --git a/library/Icingadb/Widget/ItemList/NotificationListItemMinimal.php b/library/Icingadb/Widget/ItemList/NotificationListItemMinimal.php
index d1b860ad..dcda5fd0 100644
--- a/library/Icingadb/Widget/ItemList/NotificationListItemMinimal.php
+++ b/library/Icingadb/Widget/ItemList/NotificationListItemMinimal.php
@@ -20,7 +20,7 @@ class NotificationListItemMinimal extends BaseNotificationListItem
         }
     }
 
-    protected function getStateBallSize()
+    protected function getStateBallSize(): string
     {
         return StateBall::SIZE_BIG;
     }
diff --git a/library/Icingadb/Widget/ItemList/PageSeparatorItem.php b/library/Icingadb/Widget/ItemList/PageSeparatorItem.php
index 79c88d99..9524c537 100644
--- a/library/Icingadb/Widget/ItemList/PageSeparatorItem.php
+++ b/library/Icingadb/Widget/ItemList/PageSeparatorItem.php
@@ -17,7 +17,7 @@ class PageSeparatorItem extends BaseHtmlElement
     /** @var string */
     protected $tag = 'li';
 
-    public function __construct($pageNumber)
+    public function __construct(int $pageNumber)
     {
         $this->pageNumber = $pageNumber;
     }
diff --git a/library/Icingadb/Widget/ItemList/ServiceDetailHeader.php b/library/Icingadb/Widget/ItemList/ServiceDetailHeader.php
index e0a5d003..1c477199 100644
--- a/library/Icingadb/Widget/ItemList/ServiceDetailHeader.php
+++ b/library/Icingadb/Widget/ItemList/ServiceDetailHeader.php
@@ -12,7 +12,7 @@ use ipl\Web\Widget\StateBall;
 
 class ServiceDetailHeader extends ServiceListItemMinimal
 {
-    protected function getStateBallSize()
+    protected function getStateBallSize(): string
     {
         if ($this->state->state_type === 'soft') {
             return StateBall::SIZE_MEDIUM_LARGE;
diff --git a/library/Icingadb/Widget/ItemList/ServiceList.php b/library/Icingadb/Widget/ItemList/ServiceList.php
index dcee7ee4..11febb0a 100644
--- a/library/Icingadb/Widget/ItemList/ServiceList.php
+++ b/library/Icingadb/Widget/ItemList/ServiceList.php
@@ -11,7 +11,7 @@ class ServiceList extends StateList
 {
     protected $defaultAttributes = ['class' => 'service-list'];
 
-    protected function getItemClass()
+    protected function getItemClass(): string
     {
         switch ($this->getViewMode()) {
             case 'minimal':
diff --git a/library/Icingadb/Widget/ItemList/ServiceListItem.php b/library/Icingadb/Widget/ItemList/ServiceListItem.php
index 7607ca4f..a9745817 100644
--- a/library/Icingadb/Widget/ItemList/ServiceListItem.php
+++ b/library/Icingadb/Widget/ItemList/ServiceListItem.php
@@ -11,7 +11,7 @@ class ServiceListItem extends BaseServiceListItem
 {
     use ListItemCommonLayout;
 
-    protected function getStateBallSize()
+    protected function getStateBallSize(): string
     {
         return StateBall::SIZE_LARGE;
     }
diff --git a/library/Icingadb/Widget/ItemList/ServiceListItemDetailed.php b/library/Icingadb/Widget/ItemList/ServiceListItemDetailed.php
index 42fb0adc..1f93ed48 100644
--- a/library/Icingadb/Widget/ItemList/ServiceListItemDetailed.php
+++ b/library/Icingadb/Widget/ItemList/ServiceListItemDetailed.php
@@ -22,7 +22,7 @@ class ServiceListItemDetailed extends BaseServiceListItem
     /** @var int Max pie charts to be shown */
     const PIE_CHART_LIMIT = 5;
 
-    protected function getStateBallSize()
+    protected function getStateBallSize(): string
     {
         return StateBall::SIZE_LARGE;
     }
diff --git a/library/Icingadb/Widget/ItemList/ServiceListItemMinimal.php b/library/Icingadb/Widget/ItemList/ServiceListItemMinimal.php
index 09f3fe53..e7a1bc66 100644
--- a/library/Icingadb/Widget/ItemList/ServiceListItemMinimal.php
+++ b/library/Icingadb/Widget/ItemList/ServiceListItemMinimal.php
@@ -11,7 +11,7 @@ class ServiceListItemMinimal extends BaseServiceListItem
 {
     use ListItemMinimalLayout;
 
-    protected function getStateBallSize()
+    protected function getStateBallSize(): string
     {
         return StateBall::SIZE_BIG;
     }
diff --git a/library/Icingadb/Widget/ItemList/ServicegroupList.php b/library/Icingadb/Widget/ItemList/ServicegroupList.php
index c74d0e86..fa612f1c 100644
--- a/library/Icingadb/Widget/ItemList/ServicegroupList.php
+++ b/library/Icingadb/Widget/ItemList/ServicegroupList.php
@@ -24,7 +24,7 @@ class ServicegroupList extends BaseItemList
         $this->setDetailUrl(Url::fromPath('icingadb/servicegroup'));
     }
 
-    protected function getItemClass()
+    protected function getItemClass(): string
     {
         $this->addAttributes(['class' => $this->getViewMode()]);
 
diff --git a/library/Icingadb/Widget/ItemList/StateListItem.php b/library/Icingadb/Widget/ItemList/StateListItem.php
index a8e692b7..b4fc0927 100644
--- a/library/Icingadb/Widget/ItemList/StateListItem.php
+++ b/library/Icingadb/Widget/ItemList/StateListItem.php
@@ -39,7 +39,7 @@ abstract class StateListItem extends BaseListItem
 
     abstract protected function createSubject();
 
-    abstract protected function getStateBallSize();
+    abstract protected function getStateBallSize(): string;
 
     protected function assembleCaption(BaseHtmlElement $caption)
     {
diff --git a/library/Icingadb/Widget/ItemList/UserList.php b/library/Icingadb/Widget/ItemList/UserList.php
index 5c2bc6fb..826a467f 100644
--- a/library/Icingadb/Widget/ItemList/UserList.php
+++ b/library/Icingadb/Widget/ItemList/UserList.php
@@ -22,7 +22,7 @@ class UserList extends BaseItemList
         $this->setDetailUrl(Url::fromPath('icingadb/user'));
     }
 
-    protected function getItemClass()
+    protected function getItemClass(): string
     {
         return UserListItem::class;
     }
diff --git a/library/Icingadb/Widget/ItemList/UsergroupList.php b/library/Icingadb/Widget/ItemList/UsergroupList.php
index ba4b7411..2e95368a 100644
--- a/library/Icingadb/Widget/ItemList/UsergroupList.php
+++ b/library/Icingadb/Widget/ItemList/UsergroupList.php
@@ -22,7 +22,7 @@ class UsergroupList extends BaseItemList
         $this->setDetailUrl(Url::fromPath('icingadb/usergroup'));
     }
 
-    protected function getItemClass()
+    protected function getItemClass(): string
     {
         return UsergroupListItem::class;
     }
diff --git a/library/Icingadb/Widget/MarkdownLine.php b/library/Icingadb/Widget/MarkdownLine.php
index 4019d8df..74c413d8 100644
--- a/library/Icingadb/Widget/MarkdownLine.php
+++ b/library/Icingadb/Widget/MarkdownLine.php
@@ -19,7 +19,7 @@ class MarkdownLine extends BaseHtmlElement
      *
      * @param string $line
      */
-    public function __construct($line)
+    public function __construct(string $line)
     {
         $this->add((new DeferredText(function () use ($line) {
             return Markdown::line($line);
diff --git a/library/Icingadb/Widget/MarkdownText.php b/library/Icingadb/Widget/MarkdownText.php
index 19fe5486..43db03e6 100644
--- a/library/Icingadb/Widget/MarkdownText.php
+++ b/library/Icingadb/Widget/MarkdownText.php
@@ -19,7 +19,7 @@ class MarkdownText extends BaseHtmlElement
      *
      * @param string $text
      */
-    public function __construct($text)
+    public function __construct(string $text)
     {
         $this->add((new DeferredText(function () use ($text) {
             return Markdown::text($text);
diff --git a/library/Icingadb/Widget/ServiceStateBadges.php b/library/Icingadb/Widget/ServiceStateBadges.php
index ad071eea..2f9530eb 100644
--- a/library/Icingadb/Widget/ServiceStateBadges.php
+++ b/library/Icingadb/Widget/ServiceStateBadges.php
@@ -7,20 +7,21 @@ namespace Icinga\Module\Icingadb\Widget;
 use Icinga\Module\Icingadb\Common\Links;
 use Icinga\Module\Icingadb\Common\ServiceStates;
 use Icinga\Module\Icingadb\Common\StateBadges;
+use ipl\Web\Url;
 
 class ServiceStateBadges extends StateBadges
 {
-    protected function getBaseUrl()
+    protected function getBaseUrl(): Url
     {
         return Links::services();
     }
 
-    protected function getPrefix()
+    protected function getPrefix(): string
     {
         return 'services';
     }
 
-    protected function getStateInt($state)
+    protected function getStateInt(string $state): int
     {
         return ServiceStates::int($state);
     }
diff --git a/library/Icingadb/Widget/ServiceStatusBar.php b/library/Icingadb/Widget/ServiceStatusBar.php
index e3411064..fd80835c 100644
--- a/library/Icingadb/Widget/ServiceStatusBar.php
+++ b/library/Icingadb/Widget/ServiceStatusBar.php
@@ -17,7 +17,7 @@ class ServiceStatusBar extends BaseStatusBar
         ));
     }
 
-    protected function createStateBadges()
+    protected function createStateBadges(): BaseHtmlElement
     {
         return new ServiceStateBadges($this->summary);
     }
diff --git a/library/Icingadb/Widget/ShowMore.php b/library/Icingadb/Widget/ShowMore.php
index d9f2bcc4..40f2a4da 100644
--- a/library/Icingadb/Widget/ShowMore.php
+++ b/library/Icingadb/Widget/ShowMore.php
@@ -24,26 +24,26 @@ class ShowMore extends BaseHtmlElement
 
     protected $label;
 
-    public function __construct(ResultSet $resultSet, Url $url, $label = null)
+    public function __construct(ResultSet $resultSet, Url $url, string $label = null)
     {
         $this->label = $label;
         $this->resultSet = $resultSet;
         $this->url = $url;
     }
 
-    public function setLabel($label)
+    public function setLabel(string $label): self
     {
         $this->label = $label;
 
         return $this;
     }
 
-    public function getLabel()
+    public function getLabel(): string
     {
         return $this->label ?: t('Show More');
     }
 
-    public function renderUnwrapped()
+    public function renderUnwrapped(): string
     {
         if ($this->resultSet->hasMore()) {
             return parent::renderUnwrapped();
diff --git a/library/Icingadb/Widget/StateBadge.php b/library/Icingadb/Widget/StateBadge.php
index c488f106..7cc81a91 100644
--- a/library/Icingadb/Widget/StateBadge.php
+++ b/library/Icingadb/Widget/StateBadge.php
@@ -26,7 +26,7 @@ class StateBadge extends BaseHtmlElement
      * @param string $state     Textual representation of a state
      * @param bool   $isHandled True if state is handled
      */
-    public function __construct($content, $state, $isHandled = false)
+    public function __construct($content, string $state, bool $isHandled = false)
     {
         $this->content = $content;
         $this->isHandled = $isHandled;
diff --git a/library/Icingadb/Widget/StateChange.php b/library/Icingadb/Widget/StateChange.php
index 9cf21592..b4f83b3e 100644
--- a/library/Icingadb/Widget/StateChange.php
+++ b/library/Icingadb/Widget/StateChange.php
@@ -19,7 +19,7 @@ class StateChange extends BaseHtmlElement
 
     protected $tag = 'div';
 
-    public function __construct($state, $previousState)
+    public function __construct(string $state, string $previousState)
     {
         $this->previousState = $previousState;
         $this->state = $state;
diff --git a/library/Icingadb/Widget/TagList.php b/library/Icingadb/Widget/TagList.php
index 09beb2ad..6a28a9cc 100644
--- a/library/Icingadb/Widget/TagList.php
+++ b/library/Icingadb/Widget/TagList.php
@@ -16,14 +16,14 @@ class TagList extends BaseHtmlElement
 
     protected $tag = 'div';
 
-    public function addLink($content, $url)
+    public function addLink($content, $url): self
     {
         $this->content[] = new Link($content, $url);
 
         return $this;
     }
 
-    public function hasContent()
+    public function hasContent(): bool
     {
         return ! empty($this->content);
     }