diff --git a/src/pocketmine/Player.php b/src/pocketmine/Player.php
index 012d47258..919757105 100644
--- a/src/pocketmine/Player.php
+++ b/src/pocketmine/Player.php
@@ -2063,12 +2063,12 @@ class Player extends Human implements CommandSender, ChunkLoader, ChunkListener,
 		}
 
 		$result = $item->onClickAir($this, $directionVector);
-		if($result === ItemUseResult::success()){
+		if($result === ItemUseResult::SUCCESS()){
 			$this->resetItemCooldown($item);
 			if($this->isSurvival()){
 				$this->inventory->setItemInHand($item);
 			}
-		}elseif($result === ItemUseResult::fail()){
+		}elseif($result === ItemUseResult::FAIL()){
 			$this->inventory->sendHeldItem($this);
 		}
 
@@ -2125,12 +2125,12 @@ class Player extends Human implements CommandSender, ChunkLoader, ChunkListener,
 					return false;
 				}
 				$result = $item->onReleaseUsing($this);
-				if($result === ItemUseResult::success()){
+				if($result === ItemUseResult::SUCCESS()){
 					$this->resetItemCooldown($item);
 					$this->inventory->setItemInHand($item);
 					return true;
 				}
-				if($result === ItemUseResult::fail()){
+				if($result === ItemUseResult::FAIL()){
 					$this->inventory->sendContents($this);
 					return true;
 				}
diff --git a/src/pocketmine/block/BlockFactory.php b/src/pocketmine/block/BlockFactory.php
index 77761361e..11643f7cc 100644
--- a/src/pocketmine/block/BlockFactory.php
+++ b/src/pocketmine/block/BlockFactory.php
@@ -375,7 +375,7 @@ class BlockFactory{
 		}
 		foreach($slabTypes as $type){
 			self::register($type);
-			self::register((clone $type)->setSlabType(SlabType::double())); //flattening hack
+			self::register((clone $type)->setSlabType(SlabType::DOUBLE())); //flattening hack
 		}
 
 		static $wallTypes = [
diff --git a/src/pocketmine/block/Slab.php b/src/pocketmine/block/Slab.php
index 1b34e5f5d..92cb7d791 100644
--- a/src/pocketmine/block/Slab.php
+++ b/src/pocketmine/block/Slab.php
@@ -40,23 +40,23 @@ abstract class Slab extends Transparent{
 	public function __construct(int $id, int $doubleId, int $variant = 0, ?string $name = null){
 		parent::__construct($id, $variant, $name . " Slab", $id);
 		$this->doubleId = $doubleId;
-		$this->slabType = SlabType::bottom();
+		$this->slabType = SlabType::BOTTOM();
 	}
 
 	public function getId() : int{
-		return $this->slabType === SlabType::double() ? $this->doubleId : parent::getId();
+		return $this->slabType === SlabType::DOUBLE() ? $this->doubleId : parent::getId();
 	}
 
 	protected function writeStateToMeta() : int{
-		if($this->slabType !== SlabType::double()){
-			return ($this->slabType === SlabType::top() ? 0x08 : 0);
+		if($this->slabType !== SlabType::DOUBLE()){
+			return ($this->slabType === SlabType::TOP() ? 0x08 : 0);
 		}
 		return 0;
 	}
 
 	public function readStateFromMeta(int $meta) : void{
-		if($this->slabType !== SlabType::double()){
-			$this->slabType = ($meta & 0x08) !== 0 ? SlabType::top() : SlabType::bottom();
+		if($this->slabType !== SlabType::DOUBLE()){
+			$this->slabType = ($meta & 0x08) !== 0 ? SlabType::TOP() : SlabType::BOTTOM();
 		}
 	}
 
@@ -65,7 +65,7 @@ abstract class Slab extends Transparent{
 	}
 
 	public function isTransparent() : bool{
-		return $this->slabType !== SlabType::double();
+		return $this->slabType !== SlabType::DOUBLE();
 	}
 
 	/**
@@ -92,8 +92,8 @@ abstract class Slab extends Transparent{
 			return true;
 		}
 
-		if($blockReplace instanceof Slab and $blockReplace->slabType !== SlabType::double() and $blockReplace->isSameType($this)){
-			if($blockReplace->slabType === SlabType::top()){ //Trying to combine with top slab
+		if($blockReplace instanceof Slab and $blockReplace->slabType !== SlabType::DOUBLE() and $blockReplace->isSameType($this)){
+			if($blockReplace->slabType === SlabType::TOP()){ //Trying to combine with top slab
 				return $clickVector->y <= 0.5 or (!$isClickedBlock and $face === Facing::UP);
 			}else{
 				return $clickVector->y >= 0.5 or (!$isClickedBlock and $face === Facing::DOWN);
@@ -106,35 +106,35 @@ abstract class Slab extends Transparent{
 	public function place(Item $item, Block $blockReplace, Block $blockClicked, int $face, Vector3 $clickVector, Player $player = null) : bool{
 		/* note these conditions can't be merged, since one targets clicked and the other replace */
 
-		if($blockClicked instanceof Slab and $blockClicked->slabType !== SlabType::double() and $blockClicked->isSameType($this) and (
-			($face === Facing::DOWN and $blockClicked->slabType === SlabType::top()) or
-			($face === Facing::UP and $blockClicked->slabType === SlabType::bottom())
+		if($blockClicked instanceof Slab and $blockClicked->slabType !== SlabType::DOUBLE() and $blockClicked->isSameType($this) and (
+			($face === Facing::DOWN and $blockClicked->slabType === SlabType::TOP()) or
+			($face === Facing::UP and $blockClicked->slabType === SlabType::BOTTOM())
 		)){
-			$this->slabType = SlabType::double();
+			$this->slabType = SlabType::DOUBLE();
 			return $this->level->setBlock($blockClicked, $this);
 		}
 
-		if($blockReplace instanceof Slab and $blockReplace->slabType !== SlabType::double() and $blockReplace->isSameType($this) and (
-			($blockReplace->slabType === SlabType::top() and ($clickVector->y <= 0.5 or $face === Facing::UP)) or
-			($blockReplace->slabType === SlabType::bottom() and ($clickVector->y >= 0.5 or $face === Facing::DOWN))
+		if($blockReplace instanceof Slab and $blockReplace->slabType !== SlabType::DOUBLE() and $blockReplace->isSameType($this) and (
+			($blockReplace->slabType === SlabType::TOP() and ($clickVector->y <= 0.5 or $face === Facing::UP)) or
+			($blockReplace->slabType === SlabType::BOTTOM() and ($clickVector->y >= 0.5 or $face === Facing::DOWN))
 		)){
 			//Clicked in empty half of existing slab
-			$this->slabType = SlabType::double();
+			$this->slabType = SlabType::DOUBLE();
 		}else{
-			$this->slabType = (($face !== Facing::UP && $clickVector->y > 0.5) || $face === Facing::DOWN) ? SlabType::top() : SlabType::bottom();
+			$this->slabType = (($face !== Facing::UP && $clickVector->y > 0.5) || $face === Facing::DOWN) ? SlabType::TOP() : SlabType::BOTTOM();
 		}
 
 		return parent::place($item, $blockReplace, $blockClicked, $face, $clickVector, $player);
 	}
 
 	protected function recalculateBoundingBox() : ?AxisAlignedBB{
-		if($this->slabType === SlabType::double()){
+		if($this->slabType === SlabType::DOUBLE()){
 			return parent::recalculateBoundingBox();
 		}
-		return AxisAlignedBB::one()->trim($this->slabType === SlabType::top() ? Facing::DOWN : Facing::UP, 0.5);
+		return AxisAlignedBB::one()->trim($this->slabType === SlabType::TOP() ? Facing::DOWN : Facing::UP, 0.5);
 	}
 
 	public function getDropsForCompatibleTool(Item $item) : array{
-		return [$this->getItem()->setCount($this->slabType === SlabType::double() ? 2 : 1)];
+		return [$this->getItem()->setCount($this->slabType === SlabType::DOUBLE() ? 2 : 1)];
 	}
 }
diff --git a/src/pocketmine/block/utils/SlabType.php b/src/pocketmine/block/utils/SlabType.php
index e3ba9d040..57fa535ca 100644
--- a/src/pocketmine/block/utils/SlabType.php
+++ b/src/pocketmine/block/utils/SlabType.php
@@ -30,19 +30,19 @@ final class SlabType{
 	 */
 	private $name;
 
-	public static function bottom() : self{
+	public static function BOTTOM() : self{
 		/** @var SlabType $ret */
 		static $ret = null;
 		return $ret ?? ($ret = new self("bottom"));
 	}
 
-	public static function top() : self{
+	public static function TOP() : self{
 		/** @var SlabType $ret */
 		static $ret = null;
 		return $ret ?? ($ret = new self("top"));
 	}
 
-	public static function double() : self{
+	public static function DOUBLE() : self{
 		/** @var SlabType $ret */
 		static $ret = null;
 		return $ret ?? ($ret = new self("double"));
diff --git a/src/pocketmine/item/Bow.php b/src/pocketmine/item/Bow.php
index ec694619d..f2aefa10d 100644
--- a/src/pocketmine/item/Bow.php
+++ b/src/pocketmine/item/Bow.php
@@ -49,7 +49,7 @@ class Bow extends Tool{
 
 	public function onReleaseUsing(Player $player) : ItemUseResult{
 		if($player->isSurvival() and !$player->getInventory()->contains(ItemFactory::get(Item::ARROW, 0, 1))){
-			return ItemUseResult::fail();
+			return ItemUseResult::FAIL();
 		}
 
 		$nbt = EntityFactory::createBaseNBT(
@@ -92,7 +92,7 @@ class Bow extends Tool{
 
 		if($ev->isCancelled()){
 			$entity->flagForDespawn();
-			return ItemUseResult::fail();
+			return ItemUseResult::FAIL();
 		}
 
 		$entity->setMotion($entity->getMotion()->multiply($ev->getForce()));
@@ -102,7 +102,7 @@ class Bow extends Tool{
 			$projectileEv->call();
 			if($projectileEv->isCancelled()){
 				$ev->getProjectile()->flagForDespawn();
-				return ItemUseResult::fail();
+				return ItemUseResult::FAIL();
 			}
 
 			$ev->getProjectile()->spawnToAll();
@@ -118,6 +118,6 @@ class Bow extends Tool{
 			$this->applyDamage(1);
 		}
 
-		return ItemUseResult::success();
+		return ItemUseResult::SUCCESS();
 	}
 }
diff --git a/src/pocketmine/item/Bucket.php b/src/pocketmine/item/Bucket.php
index 5a17c2de1..2b850f749 100644
--- a/src/pocketmine/item/Bucket.php
+++ b/src/pocketmine/item/Bucket.php
@@ -58,12 +58,12 @@ class Bucket extends Item{
 				}else{
 					$player->getInventory()->addItem($ev->getItem());
 				}
-				return ItemUseResult::success();
+				return ItemUseResult::SUCCESS();
 			}
 
-			return ItemUseResult::fail();
+			return ItemUseResult::FAIL();
 		}
 
-		return ItemUseResult::none();
+		return ItemUseResult::NONE();
 	}
 }
diff --git a/src/pocketmine/item/FlintSteel.php b/src/pocketmine/item/FlintSteel.php
index bb1d94dfd..4bd735a7e 100644
--- a/src/pocketmine/item/FlintSteel.php
+++ b/src/pocketmine/item/FlintSteel.php
@@ -44,10 +44,10 @@ class FlintSteel extends Tool{
 
 			$this->applyDamage(1);
 
-			return ItemUseResult::success();
+			return ItemUseResult::SUCCESS();
 		}
 
-		return ItemUseResult::none();
+		return ItemUseResult::NONE();
 	}
 
 	public function getMaxDurability() : int{
diff --git a/src/pocketmine/item/Item.php b/src/pocketmine/item/Item.php
index 743ccb81b..4f3ca5ff9 100644
--- a/src/pocketmine/item/Item.php
+++ b/src/pocketmine/item/Item.php
@@ -738,7 +738,7 @@ class Item implements ItemIds, \JsonSerializable{
 	 * @return ItemUseResult
 	 */
 	public function onActivate(Player $player, Block $blockReplace, Block $blockClicked, int $face, Vector3 $clickVector) : ItemUseResult{
-		return ItemUseResult::none();
+		return ItemUseResult::NONE();
 	}
 
 	/**
@@ -751,7 +751,7 @@ class Item implements ItemIds, \JsonSerializable{
 	 * @return ItemUseResult
 	 */
 	public function onClickAir(Player $player, Vector3 $directionVector) : ItemUseResult{
-		return ItemUseResult::none();
+		return ItemUseResult::NONE();
 	}
 
 	/**
@@ -763,7 +763,7 @@ class Item implements ItemIds, \JsonSerializable{
 	 * @return ItemUseResult
 	 */
 	public function onReleaseUsing(Player $player) : ItemUseResult{
-		return ItemUseResult::none();
+		return ItemUseResult::NONE();
 	}
 
 	/**
diff --git a/src/pocketmine/item/ItemUseResult.php b/src/pocketmine/item/ItemUseResult.php
index 78b89802c..90e8b4724 100644
--- a/src/pocketmine/item/ItemUseResult.php
+++ b/src/pocketmine/item/ItemUseResult.php
@@ -36,7 +36,7 @@ final class ItemUseResult{
 	 *
 	 * @return ItemUseResult
 	 */
-	public static function none() : ItemUseResult{
+	public static function NONE() : ItemUseResult{
 		return self::$NONE ?? (self::$NONE = new self());
 	}
 
@@ -46,7 +46,7 @@ final class ItemUseResult{
 	 *
 	 * @return ItemUseResult
 	 */
-	public static function fail() : ItemUseResult{
+	public static function FAIL() : ItemUseResult{
 		return self::$FAILED ?? (self::$FAILED = new self());
 	}
 
@@ -55,7 +55,7 @@ final class ItemUseResult{
 	 *
 	 * @return ItemUseResult
 	 */
-	public static function success() : ItemUseResult{
+	public static function SUCCESS() : ItemUseResult{
 		return self::$SUCCEEDED ?? (self::$SUCCEEDED = new self());
 	}
 
diff --git a/src/pocketmine/item/LiquidBucket.php b/src/pocketmine/item/LiquidBucket.php
index 21a76b45e..f8d9eb5e5 100644
--- a/src/pocketmine/item/LiquidBucket.php
+++ b/src/pocketmine/item/LiquidBucket.php
@@ -54,7 +54,7 @@ class LiquidBucket extends Item{
 
 	public function onActivate(Player $player, Block $blockReplace, Block $blockClicked, int $face, Vector3 $clickVector) : ItemUseResult{
 		if(!$blockReplace->canBeReplaced()){
-			return ItemUseResult::none();
+			return ItemUseResult::NONE();
 		}
 
 		//TODO: move this to generic placement logic
@@ -69,12 +69,12 @@ class LiquidBucket extends Item{
 				if($player->isSurvival()){
 					$player->getInventory()->setItemInHand($ev->getItem());
 				}
-				return ItemUseResult::success();
+				return ItemUseResult::SUCCESS();
 			}
 
-			return ItemUseResult::fail();
+			return ItemUseResult::FAIL();
 		}
 
-		return ItemUseResult::none();
+		return ItemUseResult::NONE();
 	}
 }
diff --git a/src/pocketmine/item/PaintingItem.php b/src/pocketmine/item/PaintingItem.php
index 115a462da..e577d9b49 100644
--- a/src/pocketmine/item/PaintingItem.php
+++ b/src/pocketmine/item/PaintingItem.php
@@ -40,7 +40,7 @@ class PaintingItem extends Item{
 
 	public function onActivate(Player $player, Block $blockReplace, Block $blockClicked, int $face, Vector3 $clickVector) : ItemUseResult{
 		if(Facing::axis($face) === Facing::AXIS_Y){
-			return ItemUseResult::none();
+			return ItemUseResult::NONE();
 		}
 
 		$motives = [];
@@ -68,7 +68,7 @@ class PaintingItem extends Item{
 		}
 
 		if(empty($motives)){ //No space available
-			return ItemUseResult::none();
+			return ItemUseResult::NONE();
 		}
 
 		/** @var PaintingMotive $motive */
@@ -83,7 +83,7 @@ class PaintingItem extends Item{
 
 		$direction = $directions[$face] ?? -1;
 		if($direction === -1){
-			return ItemUseResult::none();
+			return ItemUseResult::NONE();
 		}
 
 		$nbt = EntityFactory::createBaseNBT($blockReplace, null, $direction * 90, 0);
@@ -99,6 +99,6 @@ class PaintingItem extends Item{
 		$entity->spawnToAll();
 
 		$player->getLevel()->broadcastLevelEvent($blockReplace->add(0.5, 0.5, 0.5), LevelEventPacket::EVENT_SOUND_ITEMFRAME_PLACE); //item frame and painting have the same sound
-		return ItemUseResult::success();
+		return ItemUseResult::SUCCESS();
 	}
 }
diff --git a/src/pocketmine/item/ProjectileItem.php b/src/pocketmine/item/ProjectileItem.php
index 02b564d13..4208434d7 100644
--- a/src/pocketmine/item/ProjectileItem.php
+++ b/src/pocketmine/item/ProjectileItem.php
@@ -68,7 +68,7 @@ abstract class ProjectileItem extends Item{
 		$projectileEv->call();
 		if($projectileEv->isCancelled()){
 			$projectile->flagForDespawn();
-			return ItemUseResult::fail();
+			return ItemUseResult::FAIL();
 		}
 
 		$projectile->spawnToAll();
@@ -77,6 +77,6 @@ abstract class ProjectileItem extends Item{
 
 		$this->pop();
 
-		return ItemUseResult::success();
+		return ItemUseResult::SUCCESS();
 	}
 }
diff --git a/src/pocketmine/item/SpawnEgg.php b/src/pocketmine/item/SpawnEgg.php
index 364280928..6fd053a1f 100644
--- a/src/pocketmine/item/SpawnEgg.php
+++ b/src/pocketmine/item/SpawnEgg.php
@@ -61,6 +61,6 @@ class SpawnEgg extends Item{
 		$this->pop();
 		$entity->spawnToAll();
 		//TODO: what if the entity was marked for deletion?
-		return ItemUseResult::success();
+		return ItemUseResult::SUCCESS();
 	}
 }
diff --git a/src/pocketmine/level/Level.php b/src/pocketmine/level/Level.php
index 297c067bd..274a0bdf6 100644
--- a/src/pocketmine/level/Level.php
+++ b/src/pocketmine/level/Level.php
@@ -1798,8 +1798,8 @@ class Level implements ChunkManager, Metadatable{
 
 				if(!$player->isSneaking()){
 					$result = $item->onActivate($player, $blockReplace, $blockClicked, $face, $clickVector);
-					if($result !== ItemUseResult::none()){
-						return $result === ItemUseResult::success();
+					if($result !== ItemUseResult::NONE()){
+						return $result === ItemUseResult::SUCCESS();
 					}
 				}
 			}else{