diff --git a/src/pocketmine/PocketMine.php b/src/pocketmine/PocketMine.php
index fae48b793..e5c056ef6 100644
--- a/src/pocketmine/PocketMine.php
+++ b/src/pocketmine/PocketMine.php
@@ -291,7 +291,7 @@ namespace pocketmine {
 	/**
 	 * @param string $offset In the format of +09:00, +02:00, -04:00 etc.
 	 *
-	 * @return string
+	 * @return string|bool
 	 */
 	function parse_offset($offset){
 		//Make signed offsets unsigned for date_parse
diff --git a/src/pocketmine/block/Block.php b/src/pocketmine/block/Block.php
index 2bf5099d5..20c8aa624 100644
--- a/src/pocketmine/block/Block.php
+++ b/src/pocketmine/block/Block.php
@@ -680,7 +680,7 @@ class Block extends Position implements BlockIds, Metadatable{
 	 * @param Vector3 $pos1
 	 * @param Vector3 $pos2
 	 *
-	 * @return MovingObjectPosition
+	 * @return MovingObjectPosition|null
 	 */
 	public function calculateIntercept(Vector3 $pos1, Vector3 $pos2){
 		$bb = $this->getBoundingBox();
diff --git a/src/pocketmine/command/Command.php b/src/pocketmine/command/Command.php
index 65f6b5411..d0e07587f 100644
--- a/src/pocketmine/command/Command.php
+++ b/src/pocketmine/command/Command.php
@@ -139,7 +139,7 @@ abstract class Command{
 	}
 
 	/**
-	 * @return string
+	 * @return string|null
 	 */
 	public function getPermission(){
 		return $this->commandData["pocketminePermission"] ?? null;
diff --git a/src/pocketmine/command/CommandReader.php b/src/pocketmine/command/CommandReader.php
index e8bab2a84..093a4d9ee 100644
--- a/src/pocketmine/command/CommandReader.php
+++ b/src/pocketmine/command/CommandReader.php
@@ -160,7 +160,7 @@ class CommandReader extends Thread{
 	 */
 	public function getLine(){
 		if($this->buffer->count() !== 0){
-			return $this->buffer->shift();
+			return (string) $this->buffer->shift();
 		}
 
 		return null;
diff --git a/src/pocketmine/command/defaults/ParticleCommand.php b/src/pocketmine/command/defaults/ParticleCommand.php
index 0e7c5dec4..ba51cf0ed 100644
--- a/src/pocketmine/command/defaults/ParticleCommand.php
+++ b/src/pocketmine/command/defaults/ParticleCommand.php
@@ -133,7 +133,7 @@ class ParticleCommand extends VanillaCommand{
 	 * @param float    $zd
 	 * @param int|null $data
 	 *
-	 * @return Particle
+	 * @return Particle|null
 	 */
 	private function getParticle($name, Vector3 $pos, $xd, $yd, $zd, $data){
 		switch($name){
diff --git a/src/pocketmine/entity/Entity.php b/src/pocketmine/entity/Entity.php
index e95a69026..f82321ae7 100644
--- a/src/pocketmine/entity/Entity.php
+++ b/src/pocketmine/entity/Entity.php
@@ -698,7 +698,7 @@ abstract class Entity extends Location implements Metadatable{
 	 * @param CompoundTag $nbt
 	 * @param             $args
 	 *
-	 * @return Entity
+	 * @return Entity|null
 	 */
 	public static function createEntity($type, Level $level, CompoundTag $nbt, ...$args){
 		if(isset(self::$knownEntities[$type])){
@@ -1897,7 +1897,7 @@ abstract class Entity extends Location implements Metadatable{
 	/**
 	 * @param int $id
 	 *
-	 * @return int
+	 * @return int|null
 	 */
 	public function getDataPropertyType($id){
 		return isset($this->dataProperties[$id]) ? $this->dataProperties[$id][0] : null;
diff --git a/src/pocketmine/entity/Living.php b/src/pocketmine/entity/Living.php
index 1fa732c80..6e2bf3d98 100644
--- a/src/pocketmine/entity/Living.php
+++ b/src/pocketmine/entity/Living.php
@@ -328,7 +328,7 @@ abstract class Living extends Entity implements Damageable{
 	 * @param int   $maxDistance
 	 * @param array $transparent
 	 *
-	 * @return Block
+	 * @return Block|null
 	 */
 	public function getTargetBlock($maxDistance, array $transparent = []){
 		try{
diff --git a/src/pocketmine/event/Event.php b/src/pocketmine/event/Event.php
index a5e6fef75..caff3e999 100644
--- a/src/pocketmine/event/Event.php
+++ b/src/pocketmine/event/Event.php
@@ -36,7 +36,9 @@ abstract class Event{
 	 * Not doing so will deny the proper event initialization
 	 */
 
+	/** @var string|null */
 	protected $eventName = null;
+	/** @var bool */
 	private $isCancelled = false;
 
 	/**
diff --git a/src/pocketmine/event/TranslationContainer.php b/src/pocketmine/event/TranslationContainer.php
index f71ffcdaa..67c6c8ca5 100644
--- a/src/pocketmine/event/TranslationContainer.php
+++ b/src/pocketmine/event/TranslationContainer.php
@@ -48,7 +48,7 @@ class TranslationContainer extends TextContainer{
 	/**
 	 * @param int $i
 	 *
-	 * @return string
+	 * @return string|null
 	 */
 	public function getParameter($i){
 		return isset($this->params[$i]) ? $this->params[$i] : null;
diff --git a/src/pocketmine/event/entity/EntityDespawnEvent.php b/src/pocketmine/event/entity/EntityDespawnEvent.php
index c35b82bb7..2b783278f 100644
--- a/src/pocketmine/event/entity/EntityDespawnEvent.php
+++ b/src/pocketmine/event/entity/EntityDespawnEvent.php
@@ -36,6 +36,7 @@ use pocketmine\entity\Vehicle;
 class EntityDespawnEvent extends EntityEvent{
 	public static $handlerList = null;
 
+	/** @var int */
 	private $entityType;
 
 	/**
diff --git a/src/pocketmine/event/entity/EntitySpawnEvent.php b/src/pocketmine/event/entity/EntitySpawnEvent.php
index 2ef6e8bdd..cae7724e6 100644
--- a/src/pocketmine/event/entity/EntitySpawnEvent.php
+++ b/src/pocketmine/event/entity/EntitySpawnEvent.php
@@ -36,6 +36,7 @@ use pocketmine\entity\Vehicle;
 class EntitySpawnEvent extends EntityEvent{
 	public static $handlerList = null;
 
+	/** @var int */
 	private $entityType;
 
 	/**
diff --git a/src/pocketmine/event/server/LowMemoryEvent.php b/src/pocketmine/event/server/LowMemoryEvent.php
index 63151f2aa..c56e1b739 100644
--- a/src/pocketmine/event/server/LowMemoryEvent.php
+++ b/src/pocketmine/event/server/LowMemoryEvent.php
@@ -33,7 +33,9 @@ use pocketmine\utils\Utils;
 class LowMemoryEvent extends ServerEvent{
 	public static $handlerList = null;
 
+	/** @var int */
 	private $memory;
+	/** @var int */
 	private $memoryLimit;
 	private $triggerCount;
 	private $global;
@@ -60,7 +62,7 @@ class LowMemoryEvent extends ServerEvent{
 	 * @return int
 	 */
 	public function getMemoryLimit(){
-		return $this->memory;
+		return $this->memoryLimit;
 	}
 
 	/**
diff --git a/src/pocketmine/inventory/CraftingManager.php b/src/pocketmine/inventory/CraftingManager.php
index 95fd1cced..aca85258b 100644
--- a/src/pocketmine/inventory/CraftingManager.php
+++ b/src/pocketmine/inventory/CraftingManager.php
@@ -151,7 +151,7 @@ class CraftingManager{
 
 	/**
 	 * @param UUID $id
-	 * @return Recipe
+	 * @return Recipe|null
 	 */
 	public function getRecipe(UUID $id){
 		$index = $id->toBinary();
@@ -175,7 +175,7 @@ class CraftingManager{
 	/**
 	 * @param Item $input
 	 *
-	 * @return FurnaceRecipe
+	 * @return FurnaceRecipe|null
 	 */
 	public function matchFurnaceRecipe(Item $input){
 		if(isset($this->furnaceRecipes[$input->getId() . ":" . $input->getDamage()])){
diff --git a/src/pocketmine/inventory/InventoryType.php b/src/pocketmine/inventory/InventoryType.php
index a6ff58038..d29e2ba0a 100644
--- a/src/pocketmine/inventory/InventoryType.php
+++ b/src/pocketmine/inventory/InventoryType.php
@@ -51,7 +51,7 @@ class InventoryType{
 	/**
 	 * @param $index
 	 *
-	 * @return InventoryType
+	 * @return InventoryType|null
 	 */
 	public static function get($index){
 		return static::$default[$index] ?? null;
diff --git a/src/pocketmine/item/Item.php b/src/pocketmine/item/Item.php
index 14f216cee..2cad38717 100644
--- a/src/pocketmine/item/Item.php
+++ b/src/pocketmine/item/Item.php
@@ -294,7 +294,7 @@ class Item implements ItemIds, \JsonSerializable{
 	/**
 	 * @param $index
 	 *
-	 * @return Item
+	 * @return Item|null
 	 */
 	public static function getCreativeItem(int $index){
 		return Item::$creative[$index] ?? null;
diff --git a/src/pocketmine/level/Level.php b/src/pocketmine/level/Level.php
index 8c248b3a4..337b2e380 100644
--- a/src/pocketmine/level/Level.php
+++ b/src/pocketmine/level/Level.php
@@ -1848,7 +1848,7 @@ class Level implements ChunkManager, Metadatable{
 	/**
 	 * @param int $entityId
 	 *
-	 * @return Entity
+	 * @return Entity|null
 	 */
 	public function getEntity(int $entityId){
 		return $this->entities[$entityId] ?? null;
@@ -1935,7 +1935,7 @@ class Level implements ChunkManager, Metadatable{
 	/**
 	 * @param $tileId
 	 *
-	 * @return Tile
+	 * @return Tile|null
 	 */
 	public function getTileById(int $tileId){
 		return $this->tiles[$tileId] ?? null;
@@ -1962,7 +1962,7 @@ class Level implements ChunkManager, Metadatable{
 	 *
 	 * @param Vector3 $pos
 	 *
-	 * @return Tile
+	 * @return Tile|null
 	 */
 	public function getTile(Vector3 $pos){
 		$chunk = $this->getChunk($pos->x >> 4, $pos->z >> 4, false);
@@ -2196,7 +2196,7 @@ class Level implements ChunkManager, Metadatable{
 	 * @param int  $z
 	 * @param bool $create Whether to generate the chunk if it does not exist
 	 *
-	 * @return Chunk
+	 * @return Chunk|null
 	 */
 	public function getChunk(int $x, int $z, bool $create = false){
 		if(isset($this->chunks[$index = Level::chunkHash($x, $z)])){
diff --git a/src/pocketmine/level/SimpleChunkManager.php b/src/pocketmine/level/SimpleChunkManager.php
index c22cdcccc..19f088ab1 100644
--- a/src/pocketmine/level/SimpleChunkManager.php
+++ b/src/pocketmine/level/SimpleChunkManager.php
@@ -33,6 +33,12 @@ class SimpleChunkManager implements ChunkManager{
 	protected $seed;
 	protected $worldHeight;
 
+	/**
+	 * SimpleChunkManager constructor.
+	 *
+	 * @param int $seed
+	 * @param int $worldHeight
+	 */
 	public function __construct($seed, int $worldHeight = Level::Y_MAX){
 		$this->seed = $seed;
 		$this->worldHeight = $worldHeight;
diff --git a/src/pocketmine/level/format/Chunk.php b/src/pocketmine/level/format/Chunk.php
index b71fae29e..0865b28f2 100644
--- a/src/pocketmine/level/format/Chunk.php
+++ b/src/pocketmine/level/format/Chunk.php
@@ -67,12 +67,13 @@ class Chunk{
 	/** @var Entity[] */
 	protected $entities = [];
 
-	/** @var int[256] */
+	/** @var int[] */
 	protected $heightMap = [];
 
 	/** @var string */
 	protected $biomeIds;
 
+	/** @var int[] */
 	protected $extraData = [];
 
 	/** @var CompoundTag[] */
diff --git a/src/pocketmine/level/format/io/region/McRegion.php b/src/pocketmine/level/format/io/region/McRegion.php
index c23af793d..c8778a2a0 100644
--- a/src/pocketmine/level/format/io/region/McRegion.php
+++ b/src/pocketmine/level/format/io/region/McRegion.php
@@ -430,7 +430,7 @@ class McRegion extends BaseLevelProvider{
 	 * @param int $x
 	 * @param int $z
 	 *
-	 * @return RegionLoader
+	 * @return RegionLoader|null
 	 */
 	protected function getRegion(int $x, int $z){
 		return $this->regions[Level::chunkHash($x, $z)] ?? null;
diff --git a/src/pocketmine/math/Vector3.php b/src/pocketmine/math/Vector3.php
index e572d2166..b5b8515ee 100644
--- a/src/pocketmine/math/Vector3.php
+++ b/src/pocketmine/math/Vector3.php
@@ -245,7 +245,7 @@ class Vector3{
 	 * @param Vector3 $v
 	 * @param float   $x
 	 *
-	 * @return Vector3
+	 * @return Vector3|null
 	 */
 	public function getIntermediateWithXValue(Vector3 $v, $x){
 		$xDiff = $v->x - $this->x;
@@ -272,7 +272,7 @@ class Vector3{
 	 * @param Vector3 $v
 	 * @param float   $y
 	 *
-	 * @return Vector3
+	 * @return Vector3|null
 	 */
 	public function getIntermediateWithYValue(Vector3 $v, $y){
 		$xDiff = $v->x - $this->x;
@@ -299,7 +299,7 @@ class Vector3{
 	 * @param Vector3 $v
 	 * @param float   $z
 	 *
-	 * @return Vector3
+	 * @return Vector3|null
 	 */
 	public function getIntermediateWithZValue(Vector3 $v, $z){
 		$xDiff = $v->x - $this->x;
diff --git a/src/pocketmine/permission/BanEntry.php b/src/pocketmine/permission/BanEntry.php
index 4d04bd653..fd952e668 100644
--- a/src/pocketmine/permission/BanEntry.php
+++ b/src/pocketmine/permission/BanEntry.php
@@ -104,9 +104,9 @@ class BanEntry{
 	/**
 	 * @param string $str
 	 *
-	 * @return BanEntry
+	 * @return BanEntry|null
 	 */
-	public static function fromString($str){
+	public static function fromString(string $str){
 		if(strlen($str) < 2){
 			return null;
 		}else{
diff --git a/src/pocketmine/plugin/PharPluginLoader.php b/src/pocketmine/plugin/PharPluginLoader.php
index 6c35e145a..5e7b79241 100644
--- a/src/pocketmine/plugin/PharPluginLoader.php
+++ b/src/pocketmine/plugin/PharPluginLoader.php
@@ -47,7 +47,7 @@ class PharPluginLoader implements PluginLoader{
 	 *
 	 * @param string $file
 	 *
-	 * @return Plugin
+	 * @return Plugin|null
 	 *
 	 * @throws \Exception
 	 */
@@ -80,7 +80,7 @@ class PharPluginLoader implements PluginLoader{
 	 *
 	 * @param string $file
 	 *
-	 * @return PluginDescription
+	 * @return PluginDescription|null
 	 */
 	public function getPluginDescription($file){
 		$phar = new \Phar($file);
diff --git a/src/pocketmine/plugin/Plugin.php b/src/pocketmine/plugin/Plugin.php
index befe5a541..3c22f091e 100644
--- a/src/pocketmine/plugin/Plugin.php
+++ b/src/pocketmine/plugin/Plugin.php
@@ -45,6 +45,9 @@ interface Plugin extends CommandExecutor{
 	 */
 	public function onEnable();
 
+	/**
+	 * @return bool
+	 */
 	public function isEnabled();
 
 	/**
diff --git a/src/pocketmine/plugin/PluginBase.php b/src/pocketmine/plugin/PluginBase.php
index 63b2d4d66..b6f0c7fb7 100644
--- a/src/pocketmine/plugin/PluginBase.php
+++ b/src/pocketmine/plugin/PluginBase.php
@@ -137,7 +137,7 @@ abstract class PluginBase implements Plugin{
 	/**
 	 * @param string $name
 	 *
-	 * @return Command|PluginIdentifiableCommand
+	 * @return Command|PluginIdentifiableCommand|null
 	 */
 	public function getCommand($name){
 		$command = $this->getServer()->getPluginCommand($name);
@@ -177,7 +177,7 @@ abstract class PluginBase implements Plugin{
 	 *
 	 * @param string $filename
 	 *
-	 * @return resource Resource data, or null
+	 * @return resource|null Resource data, or null
 	 */
 	public function getResource($filename){
 		$filename = rtrim(str_replace("\\", "/", $filename), "/");
diff --git a/src/pocketmine/plugin/ScriptPluginLoader.php b/src/pocketmine/plugin/ScriptPluginLoader.php
index c96511e8d..05f2524d8 100644
--- a/src/pocketmine/plugin/ScriptPluginLoader.php
+++ b/src/pocketmine/plugin/ScriptPluginLoader.php
@@ -48,7 +48,7 @@ class ScriptPluginLoader implements PluginLoader{
 	 *
 	 * @param string $file
 	 *
-	 * @return Plugin
+	 * @return Plugin|null
 	 *
 	 * @throws \Exception
 	 */
@@ -82,7 +82,7 @@ class ScriptPluginLoader implements PluginLoader{
 	 *
 	 * @param string $file
 	 *
-	 * @return PluginDescription
+	 * @return PluginDescription|null
 	 */
 	public function getPluginDescription($file){
 		$content = file($file, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
diff --git a/src/pocketmine/tile/Chest.php b/src/pocketmine/tile/Chest.php
index c3df50689..46e1fd471 100644
--- a/src/pocketmine/tile/Chest.php
+++ b/src/pocketmine/tile/Chest.php
@@ -225,7 +225,7 @@ class Chest extends Spawnable implements InventoryHolder, Container, Nameable{
 	}
 
 	/**
-	 * @return Chest
+	 * @return Chest|null
 	 */
 	public function getPair(){
 		if($this->isPaired()){
diff --git a/src/pocketmine/tile/Tile.php b/src/pocketmine/tile/Tile.php
index 1138addd6..667ecf7b1 100644
--- a/src/pocketmine/tile/Tile.php
+++ b/src/pocketmine/tile/Tile.php
@@ -82,7 +82,7 @@ abstract class Tile extends Position{
 	 * @param CompoundTag $nbt
 	 * @param             $args
 	 *
-	 * @return Tile
+	 * @return Tile|null
 	 */
 	public static function createTile($type, Level $level, CompoundTag $nbt, ...$args){
 		if(isset(self::$knownTiles[$type])){
diff --git a/src/pocketmine/utils/Utils.php b/src/pocketmine/utils/Utils.php
index ce8762fb4..d128f5168 100644
--- a/src/pocketmine/utils/Utils.php
+++ b/src/pocketmine/utils/Utils.php
@@ -36,6 +36,7 @@ class Utils{
 	public static $online = true;
 	public static $ip = false;
 	public static $os;
+	/** @var UUID|null */
 	private static $serverUniqueId = null;
 
 	/**