Modernize private static property declarations

src/entity/Entity.php

@@ -80,8 +80,7 @@ abstract class Entity{
 	public const MOTION_THRESHOLD = 0.00001;
 	protected const STEP_CLIP_MULTIPLIER = 0.4;
 
-	/** @var int */
-	private static $entityCount = 1;
+	private static int $entityCount = 1;
 
 	/**
 	 * Returns a new runtime entity ID for a new entity.

src/event/Event.php

@@ -30,8 +30,8 @@ use function get_class;
 
 abstract class Event{
 	private const MAX_EVENT_CALL_DEPTH = 50;
-	/** @var int */
-	private static $eventCallDepth = 1;
+
+	private static int $eventCallDepth = 1;
 
 	/** @var string|null */
 	protected $eventName = null;

src/network/mcpe/cache/ChunkCache.php

@@ -39,7 +39,7 @@ use function strlen;
  */
 class ChunkCache implements ChunkListener{
 	/** @var self[][] */
-	private static $instances = [];
+	private static array $instances = [];
 
 	/**
 	 * Fetches the ChunkCache instance for the given world. This lazily creates cache systems as needed.

src/network/mcpe/convert/SkinAdapterSingleton.php

@@ -27,8 +27,7 @@ namespace pocketmine\network\mcpe\convert;
  * Accessor for SkinAdapter
  */
 class SkinAdapterSingleton{
-	/** @var SkinAdapter|null */
-	private static $skinAdapter = null;
+	private static ?SkinAdapter $skinAdapter = null;
 
 	public static function get() : SkinAdapter{
 		if(self::$skinAdapter === null){

src/permission/PermissionManager.php

@@ -27,8 +27,7 @@ use function count;
 use function spl_object_id;
 
 class PermissionManager{
-	/** @var PermissionManager|null */
-	private static $instance = null;
+	private static ?self $instance = null;
 
 	public static function getInstance() : PermissionManager{
 		if(self::$instance === null){

src/thread/ThreadManager.php

@@ -27,8 +27,7 @@ use function spl_object_id;
 
 class ThreadManager extends \Volatile{
 
-	/** @var ThreadManager|null */
-	private static $instance = null;
+	private static ?self $instance = null;
 
 	public static function init() : void{
 		self::$instance = new ThreadManager();