diff --git a/Controller/BackendController.php b/Controller/BackendController.php
index 151146b..f87d6b3 100644
--- a/Controller/BackendController.php
+++ b/Controller/BackendController.php
@@ -74,7 +74,7 @@ final class BackendController extends Controller
      * @var string[]
      * @since 1.0.0
      */
-    protected static $providing = [];
+    protected static array $providing = [];
 
     /**
      * Dependencies.
@@ -82,7 +82,7 @@ final class BackendController extends Controller
      * @var string[]
      * @since 1.0.0
      */
-    protected static $dependencies = [];
+    protected static array $dependencies = [];
 
     /**
      * @param RequestAbstract  $request  Request
diff --git a/Controller/Controller.php b/Controller/Controller.php
index 24ca383..d5c5026 100644
--- a/Controller/Controller.php
+++ b/Controller/Controller.php
@@ -66,7 +66,7 @@ class Controller extends ModuleAbstract implements WebInterface
      * @var string[]
      * @since 1.0.0
      */
-    protected static $providing = [];
+    protected static array $providing = [];
 
     /**
      * Dependencies.
@@ -74,5 +74,5 @@ class Controller extends ModuleAbstract implements WebInterface
      * @var string[]
      * @since 1.0.0
      */
-    protected static $dependencies = [];
+    protected static array $dependencies = [];
 }
diff --git a/Models/CollectionMapper.php b/Models/CollectionMapper.php
index 3a65377..718500d 100644
--- a/Models/CollectionMapper.php
+++ b/Models/CollectionMapper.php
@@ -30,7 +30,7 @@ final class CollectionMapper extends MediaMapper
      * @var array<string, array<string, null|string>>
      * @since 1.0.0
      */
-    protected static $hasMany = [
+    protected static array $hasMany = [
         'sources' => [
             'mapper' => MediaMapper::class, /* mapper of the related object */
             'table'  => 'media_relation', /* table of the related object, null if no relation table is used (many->1) */
@@ -45,7 +45,7 @@ final class CollectionMapper extends MediaMapper
      * @var string
      * @since 1.0.0
      */
-    protected static $table = 'media';
+    protected static string $table = 'media';
 
     /**
      * Created at.
@@ -53,7 +53,7 @@ final class CollectionMapper extends MediaMapper
      * @var string
      * @since 1.0.0
      */
-    protected static $createdAt = 'media_created_at';
+    protected static string $createdAt = 'media_created_at';
 
     /**
      * Primary field name.
@@ -61,5 +61,5 @@ final class CollectionMapper extends MediaMapper
      * @var string
      * @since 1.0.0
      */
-    protected static $primaryField = 'media_id';
+    protected static string $primaryField = 'media_id';
 }
diff --git a/Models/Media.php b/Models/Media.php
index 2584aec..7792d8c 100644
--- a/Models/Media.php
+++ b/Models/Media.php
@@ -68,7 +68,7 @@ class Media implements \JsonSerializable
     /**
      * Uploaded.
      *
-     * @var \DateTime
+     * @var null|\DateTime
      * @since 1.0.0
      */
     protected $createdAt = null;
diff --git a/Models/MediaMapper.php b/Models/MediaMapper.php
index be36300..b97f7e3 100644
--- a/Models/MediaMapper.php
+++ b/Models/MediaMapper.php
@@ -35,7 +35,7 @@ class MediaMapper extends DataMapperAbstract
      * @since 1.0.0
      * @todo: maybe add file name for searching by file name (path in media_file should not matter for search)
      */
-    protected static $columns = [
+    protected static array $columns = [
         'media_id'              => ['name' => 'media_id', 'type' => 'int', 'internal' => 'id'],
         'media_name'            => ['name' => 'media_name', 'type' => 'string', 'internal' => 'name', 'autocomplete' => true],
         'media_description'     => ['name' => 'media_description', 'type' => 'string', 'internal' => 'description', 'autocomplete' => true],
@@ -56,7 +56,7 @@ class MediaMapper extends DataMapperAbstract
      * @var array<string, array<string, string>>
      * @since 1.0.0
      */
-    protected static $belongsTo = [
+    protected static array $belongsTo = [
         'createdBy' => [
             'mapper' => AccountMapper::class,
             'dest'   => 'media_created_by',
@@ -69,7 +69,7 @@ class MediaMapper extends DataMapperAbstract
      * @var string
      * @since 1.0.0
      */
-    protected static $table = 'media';
+    protected static string $table = 'media';
 
     /**
      * Created at.
@@ -77,7 +77,7 @@ class MediaMapper extends DataMapperAbstract
      * @var string
      * @since 1.0.0
      */
-    protected static $createdAt = 'media_created_at';
+    protected static string $createdAt = 'media_created_at';
 
     /**
      * Primary field name.
@@ -85,7 +85,7 @@ class MediaMapper extends DataMapperAbstract
      * @var string
      * @since 1.0.0
      */
-    protected static $primaryField = 'media_id';
+    protected static string $primaryField = 'media_id';
 
     /**
      * Get media based on virtual path.