diff --git a/src/pocketmine/inventory/AnvilInventory.php b/src/pocketmine/inventory/AnvilInventory.php
index e27e3e540..7b09a34aa 100644
--- a/src/pocketmine/inventory/AnvilInventory.php
+++ b/src/pocketmine/inventory/AnvilInventory.php
@@ -49,6 +49,7 @@ class AnvilInventory extends ContainerInventory{
 	}
 
 	/**
+	 * This override is here for documentation and code completion purposes only.
 	 * @return FakeBlockMenu
 	 */
 	public function getHolder(){
diff --git a/src/pocketmine/inventory/BaseInventory.php b/src/pocketmine/inventory/BaseInventory.php
index f3cca50d1..fd1663801 100644
--- a/src/pocketmine/inventory/BaseInventory.php
+++ b/src/pocketmine/inventory/BaseInventory.php
@@ -36,13 +36,11 @@ abstract class BaseInventory implements Inventory{
 
 	/** @var int */
 	protected $maxStackSize = Inventory::MAX_STACK;
-	/** @var int */
-	protected $size;
 	/** @var string */
 	protected $name;
 	/** @var string */
 	protected $title;
-	/** @var Item[] */
+	/** @var \SplFixedArray<Item> */
 	protected $slots = [];
 	/** @var Player[] */
 	protected $viewers = [];
@@ -58,7 +56,7 @@ abstract class BaseInventory implements Inventory{
 	public function __construct(InventoryHolder $holder, array $items = [], int $size = null, string $title = null){
 		$this->holder = $holder;
 
-		$this->size = $size ?? $this->getDefaultSize();
+		$this->slots = new \SplFixedArray($size ?? $this->getDefaultSize());
 		$this->title = $title ?? $this->getName();
 
 		$this->setContents($items);
@@ -76,12 +74,22 @@ abstract class BaseInventory implements Inventory{
 	 */
 	abstract public function getNetworkType() : int;
 
+	/**
+	 * Returns the size of the inventory.
+	 * @return int
+	 */
 	public function getSize() : int{
-		return $this->size;
+		return $this->slots->getSize();
 	}
 
+	/**
+	 * Sets the new size of the inventory.
+	 * WARNING: If the size is smaller, any items past the new size will be lost.
+	 *
+	 * @param int $size
+	 */
 	public function setSize(int $size){
-		$this->size = $size;
+		$this->slots->setSize($size);
 	}
 
 	abstract public function getDefaultSize() : int;
@@ -91,41 +99,41 @@ abstract class BaseInventory implements Inventory{
 	}
 
 	public function getItem(int $index) : Item{
-		assert($index >= 0, "Inventory slot should not be negative");
-		return isset($this->slots[$index]) ? clone $this->slots[$index] : Item::get(Item::AIR, 0, 0);
+		return $this->slots[$index] !== null ? clone $this->slots[$index] : Item::get(Item::AIR, 0, 0);
 	}
 
 	public function getContents() : array{
-		return $this->slots;
+		return $this->slots->toArray();
 	}
 
 	/**
 	 * @param Item[] $items
 	 */
 	public function setContents(array $items){
-		if(count($items) > $this->size){
-			$items = array_slice($items, 0, $this->size, true);
+		if(count($items) > $this->getSize()){
+			$items = array_slice($items, 0, $this->getSize(), true);
 		}
 
-		for($i = 0; $i < $this->size; ++$i){
+		for($i = 0, $size = $this->getSize(); $i < $size; ++$i){
 			if(!isset($items[$i])){
-				if(isset($this->slots[$i])){
-					$this->clear($i);
+				if($this->slots[$i] !== null){
+					$this->clear($i, false);
 				}
 			}else{
-				if(!$this->setItem($i, $items[$i])){
-					$this->clear($i);
+				if(!$this->setItem($i, $items[$i], false)){
+					$this->clear($i, false);
 				}
 			}
 		}
+
+		$this->sendContents($this->getViewers());
 	}
 
-	public function setItem(int $index, Item $item) : bool{
-		$item = clone $item;
-		if($index < 0 or $index >= $this->size){
-			return false;
-		}elseif($item->getId() === 0 or $item->getCount() <= 0){
-			return $this->clear($index);
+	public function setItem(int $index, Item $item, bool $send = true) : bool{
+		if($item->isNull()){
+			$item = Item::get(Item::AIR, 0, 0);
+		}else{
+			$item = clone $item;
 		}
 
 		$holder = $this->getHolder();
@@ -139,8 +147,8 @@ abstract class BaseInventory implements Inventory{
 		}
 
 		$old = $this->getItem($index);
-		$this->slots[$index] = clone $item;
-		$this->onSlotChange($index, $old);
+		$this->slots[$index] = $item->isNull() ? null : $item;
+		$this->onSlotChange($index, $old, $send);
 
 		return true;
 	}
@@ -200,8 +208,8 @@ abstract class BaseInventory implements Inventory{
 	}
 
 	public function firstEmpty() : int{
-		for($i = 0; $i < $this->size; ++$i){
-			if($this->getItem($i)->getId() === Item::AIR){
+		foreach($this->slots as $i => $slot){
+			if($slot === null or $slot->isNull()){
 				return $i;
 			}
 		}
@@ -324,35 +332,16 @@ abstract class BaseInventory implements Inventory{
 		return $itemSlots;
 	}
 
-	public function clear(int $index) : bool{
-		if(isset($this->slots[$index])){
-			$item = Item::get(Item::AIR, 0, 0);
-			$old = $this->slots[$index];
-			$holder = $this->getHolder();
-			if($holder instanceof Entity){
-				Server::getInstance()->getPluginManager()->callEvent($ev = new EntityInventoryChangeEvent($holder, $old, $item, $index));
-				if($ev->isCancelled()){
-					$this->sendSlot($index, $this->getViewers());
-					return false;
-				}
-				$item = $ev->getNewItem();
-			}
-			if($item->getId() !== Item::AIR){
-				$this->slots[$index] = clone $item;
-			}else{
-				unset($this->slots[$index]);
-			}
-
-			$this->onSlotChange($index, $old);
-		}
-
-		return true;
+	public function clear(int $index, bool $send = true) : bool{
+		return $this->setItem($index, Item::get(Item::AIR, 0, 0), $send);
 	}
 
 	public function clearAll(){
-		foreach($this->getContents() as $index => $i){
-			$this->clear($index);
+		for($i = 0, $size = $this->getSize(); $i < $size; ++$i){
+			$this->clear($i, false);
 		}
+
+		$this->sendContents($this->getViewers());
 	}
 
 	/**
@@ -392,8 +381,10 @@ abstract class BaseInventory implements Inventory{
 		unset($this->viewers[spl_object_hash($who)]);
 	}
 
-	public function onSlotChange($index, $before){
-		$this->sendSlot($index, $this->getViewers());
+	public function onSlotChange(int $index, Item $before, bool $send){
+		if($send){
+			$this->sendSlot($index, $this->getViewers());
+		}
 	}
 
 
@@ -424,7 +415,7 @@ abstract class BaseInventory implements Inventory{
 	 * @param int             $index
 	 * @param Player|Player[] $target
 	 */
-	public function sendSlot($index, $target){
+	public function sendSlot(int $index, $target){
 		if($target instanceof Player){
 			$target = [$target];
 		}
diff --git a/src/pocketmine/inventory/ChestInventory.php b/src/pocketmine/inventory/ChestInventory.php
index 283423b1c..d6b60e58a 100644
--- a/src/pocketmine/inventory/ChestInventory.php
+++ b/src/pocketmine/inventory/ChestInventory.php
@@ -55,6 +55,7 @@ class ChestInventory extends ContainerInventory{
 	}
 
 	/**
+	 * This override is here for documentation and code completion purposes only.
 	 * @return Chest
 	 */
 	public function getHolder(){
diff --git a/src/pocketmine/inventory/DoubleChestInventory.php b/src/pocketmine/inventory/DoubleChestInventory.php
index 142d6e3d0..b0af82759 100644
--- a/src/pocketmine/inventory/DoubleChestInventory.php
+++ b/src/pocketmine/inventory/DoubleChestInventory.php
@@ -54,6 +54,9 @@ class DoubleChestInventory extends ChestInventory implements InventoryHolder{
 		return $this;
 	}
 
+	/**
+	 * @return Chest
+	 */
 	public function getHolder(){
 		return $this->left->getHolder();
 	}
@@ -62,17 +65,17 @@ class DoubleChestInventory extends ChestInventory implements InventoryHolder{
 		return $index < $this->left->getSize() ? $this->left->getItem($index) : $this->right->getItem($index - $this->right->getSize());
 	}
 
-	public function setItem(int $index, Item $item) : bool{
-		return $index < $this->left->getSize() ? $this->left->setItem($index, $item) : $this->right->setItem($index - $this->right->getSize(), $item);
+	public function setItem(int $index, Item $item, bool $send = true) : bool{
+		return $index < $this->left->getSize() ? $this->left->setItem($index, $item, $send) : $this->right->setItem($index - $this->right->getSize(), $item, $send);
 	}
 
-	public function clear(int $index) : bool{
-		return $index < $this->left->getSize() ? $this->left->clear($index) : $this->right->clear($index - $this->right->getSize());
+	public function clear(int $index, bool $send = true) : bool{
+		return $index < $this->left->getSize() ? $this->left->clear($index, $send) : $this->right->clear($index - $this->right->getSize(), $send);
 	}
 
 	public function getContents() : array{
 		$contents = [];
-		for($i = 0; $i < $this->getSize(); ++$i){
+		for($i = 0, $size = $this->getSize(); $i < $size; ++$i){
 			$contents[$i] = $this->getItem($i);
 		}
 
@@ -83,24 +86,24 @@ class DoubleChestInventory extends ChestInventory implements InventoryHolder{
 	 * @param Item[] $items
 	 */
 	public function setContents(array $items){
-		if(count($items) > $this->size){
-			$items = array_slice($items, 0, $this->size, true);
+		$size = $this->getSize();
+		if(count($items) > $size){
+			$items = array_slice($items, 0, $size, true);
 		}
 
+		$leftSize = $this->left->getSize();
 
-		for($i = 0; $i < $this->size; ++$i){
+		for($i = 0; $i < $size; ++$i){
 			if(!isset($items[$i])){
-				if($i < $this->left->size){
-					if(isset($this->left->slots[$i])){
-						$this->clear($i);
-					}
-				}elseif(isset($this->right->slots[$i - $this->left->size])){
-					$this->clear($i);
+				if(($i < $leftSize and isset($this->left->slots[$i])) or isset($this->right->slots[$i - $leftSize])){
+					$this->clear($i, false);
 				}
-			}elseif(!$this->setItem($i, $items[$i])){
-				$this->clear($i);
+			}elseif(!$this->setItem($i, $items[$i], false)){
+				$this->clear($i, false);
 			}
 		}
+
+		$this->sendContents($this->getViewers());
 	}
 
 	public function onOpen(Player $who){
diff --git a/src/pocketmine/inventory/EnchantInventory.php b/src/pocketmine/inventory/EnchantInventory.php
index 38f6290b7..7d91bdadb 100644
--- a/src/pocketmine/inventory/EnchantInventory.php
+++ b/src/pocketmine/inventory/EnchantInventory.php
@@ -49,6 +49,7 @@ class EnchantInventory extends ContainerInventory{
 	}
 
 	/**
+	 * This override is here for documentation and code completion purposes only.
 	 * @return FakeBlockMenu
 	 */
 	public function getHolder(){
diff --git a/src/pocketmine/inventory/FurnaceInventory.php b/src/pocketmine/inventory/FurnaceInventory.php
index 7d2a8bec3..74d2a72f4 100644
--- a/src/pocketmine/inventory/FurnaceInventory.php
+++ b/src/pocketmine/inventory/FurnaceInventory.php
@@ -48,6 +48,7 @@ class FurnaceInventory extends ContainerInventory{
 	}
 
 	/**
+	 * This override is here for documentation and code completion purposes only.
 	 * @return Furnace
 	 */
 	public function getHolder(){
@@ -102,8 +103,8 @@ class FurnaceInventory extends ContainerInventory{
 		return $this->setItem(0, $item);
 	}
 
-	public function onSlotChange($index, $before){
-		parent::onSlotChange($index, $before);
+	public function onSlotChange(int $index, Item $before, bool $send){
+		parent::onSlotChange($index, $before, $send);
 
 		$this->getHolder()->scheduleUpdate();
 	}
diff --git a/src/pocketmine/inventory/Inventory.php b/src/pocketmine/inventory/Inventory.php
index 1dfcbb784..48a3779f5 100644
--- a/src/pocketmine/inventory/Inventory.php
+++ b/src/pocketmine/inventory/Inventory.php
@@ -70,10 +70,11 @@ interface Inventory{
 	 *
 	 * @param int  $index
 	 * @param Item $item
+	 * @param bool $send
 	 *
 	 * @return bool
 	 */
-	public function setItem(int $index, Item $item) : bool;
+	public function setItem(int $index, Item $item, bool $send = true) : bool;
 
 	/**
 	 * Stores the given Items in the inventory. This will try to fill
@@ -125,7 +126,7 @@ interface Inventory{
 	 * @param int             $index
 	 * @param Player|Player[] $target
 	 */
-	public function sendSlot($index, $target);
+	public function sendSlot(int $index, $target);
 
 	/**
 	 * Checks if the inventory contains any Item with the same material data.
@@ -174,11 +175,12 @@ interface Inventory{
 	/**
 	 * Will clear a specific slot
 	 *
-	 * @param int $index
+	 * @param int  $index
+	 * @param bool $send
 	 *
 	 * @return bool
 	 */
-	public function clear(int $index) : bool;
+	public function clear(int $index, bool $send = true) : bool;
 
 	/**
 	 * Clears all the slots
@@ -222,6 +224,7 @@ interface Inventory{
 	/**
 	 * @param int  $index
 	 * @param Item $before
+	 * @param bool $send
 	 */
-	public function onSlotChange($index, $before);
+	public function onSlotChange(int $index, Item $before, bool $send);
 }
diff --git a/src/pocketmine/inventory/PlayerInventory.php b/src/pocketmine/inventory/PlayerInventory.php
index b02567ea7..e5631e864 100644
--- a/src/pocketmine/inventory/PlayerInventory.php
+++ b/src/pocketmine/inventory/PlayerInventory.php
@@ -40,8 +40,11 @@ use pocketmine\Server;
 
 class PlayerInventory extends BaseInventory{
 
+	/** @var Human */
+	protected $holder;
+
 	protected $itemInHandIndex = 0;
-	/** @var int[] */
+	/** @var \SplFixedArray<int> */
 	protected $hotbar;
 
 	public function __construct(Human $player){
@@ -74,12 +77,12 @@ class PlayerInventory extends BaseInventory{
 	 * Called when a client equips a hotbar slot. This method should not be used by plugins.
 	 * This method will call PlayerItemHeldEvent.
 	 *
-	 * @param int      $hotbarSlot Number of the hotbar slot to equip.
+	 * @param int $hotbarSlot Number of the hotbar slot to equip.
 	 * @param int|null $inventorySlot Inventory slot to map to the specified hotbar slot. Supply null to make no change to the link.
 	 *
 	 * @return bool if the equipment change was successful, false if not.
 	 */
-	public function equipItem(int $hotbarSlot, $inventorySlot = null) : bool{
+	public function equipItem(int $hotbarSlot, int $inventorySlot = null) : bool{
 		if($inventorySlot === null){
 			$inventorySlot = $this->getHotbarSlotIndex($hotbarSlot);
 		}
@@ -110,11 +113,12 @@ class PlayerInventory extends BaseInventory{
 
 	/**
 	 * Returns the index of the inventory slot mapped to the specified hotbar slot, or -1 if the hotbar slot does not exist.
+	 *
 	 * @param int $index
 	 *
 	 * @return int
 	 */
-	public function getHotbarSlotIndex($index){
+	public function getHotbarSlotIndex(int $index) : int{
 		return $this->hotbar[$index] ?? -1;
 	}
 
@@ -126,15 +130,16 @@ class PlayerInventory extends BaseInventory{
 	 *
 	 * @param int $hotbarSlot
 	 * @param int $inventorySlot
+	 *
+	 * @throws \RuntimeException if the hotbar slot is out of range
+	 * @throws \InvalidArgumentException if the inventory slot is out of range
 	 */
-	public function setHotbarSlotIndex($hotbarSlot, $inventorySlot){
-		if($hotbarSlot < 0 or $hotbarSlot >= $this->getHotbarSize()){
-			throw new \InvalidArgumentException("Hotbar slot index \"$hotbarSlot\" is out of range");
-		}elseif($inventorySlot < -1 or $inventorySlot >= $this->getSize()){
+	public function setHotbarSlotIndex(int $hotbarSlot, int $inventorySlot){
+		if($inventorySlot < -1 or $inventorySlot >= $this->getSize()){
 			throw new \InvalidArgumentException("Inventory slot index \"$inventorySlot\" is out of range");
 		}
 
-		if($inventorySlot !== -1 and ($alreadyEquippedIndex = array_search($inventorySlot, $this->hotbar)) !== false){
+		if($inventorySlot !== -1 and ($alreadyEquippedIndex = array_search($inventorySlot, $this->getHotbar(), true)) !== false){
 			/* Swap the slots
 			 * This assumes that the equipped slot can only be equipped in one other slot
 			 * it will not account for ancient bugs where the same slot ended up linked to several hotbar slots.
@@ -161,35 +166,49 @@ class PlayerInventory extends BaseInventory{
 		}
 	}
 
+	public function getHotbar() : array{
+		return $this->hotbar->toArray();
+	}
+
 	/**
 	 * Resets hotbar links to their original defaults.
 	 * @param bool $send Whether to send changes to the holder.
 	 */
 	public function resetHotbar(bool $send = true){
-		$this->hotbar = range(0, $this->getHotbarSize() - 1, 1);
+		$this->hotbar = \SplFixedArray::fromArray(range(0, $this->getHotbarSize() - 1, 1));
 		if($send){
 			$this->sendContents($this->getHolder());
 		}
 	}
 
+	public function sendHotbar(){
+		$pk = new PlayerHotbarPacket();
+		$pk->windowId = ContainerIds::INVENTORY;
+		$pk->selectedSlot = $this->getHeldItemIndex();
+		$pk->slots = array_map(function(int $link){ return $link + $this->getHotbarSize(); }, $this->getHotbar());
+		$this->getHolder()->dataPacket($pk);
+	}
+
 	/**
 	 * Returns the hotbar slot number the holder is currently holding.
 	 * @return int
 	 */
-	public function getHeldItemIndex(){
+	public function getHeldItemIndex() : int{
 		return $this->itemInHandIndex;
 	}
 
 	/**
 	 * Sets which hotbar slot the player is currently loading.
 	 *
-	 * @param int  $index 0-8 index of the hotbar slot to hold
-	 * @param bool $send  Whether to send updates back to the inventory holder. This should usually be true for plugin calls.
+	 * @param int  $hotbarSlot 0-8 index of the hotbar slot to hold
+	 * @param bool $send Whether to send updates back to the inventory holder. This should usually be true for plugin calls.
 	 *                    It should only be false to prevent feedback loops of equipment packets between client and server.
+	 *
+	 * @throws \InvalidArgumentException if the hotbar slot is out of range
 	 */
-	public function setHeldItemIndex($index, $send = true){
-		if($index >= 0 and $index < $this->getHotbarSize()){
-			$this->itemInHandIndex = $index;
+	public function setHeldItemIndex(int $hotbarSlot, bool $send = true){
+		if($hotbarSlot >= 0 and $hotbarSlot < $this->getHotbarSize()){
+			$this->itemInHandIndex = $hotbarSlot;
 
 			if($this->getHolder() instanceof Player and $send){
 				$this->sendHeldItem($this->getHolder());
@@ -197,7 +216,7 @@ class PlayerInventory extends BaseInventory{
 
 			$this->sendHeldItem($this->getHolder()->getViewers());
 		}else{
-			throw new \InvalidArgumentException("Hotbar slot index \"$index\" is out of range");
+			throw new \InvalidArgumentException("Hotbar slot index \"$hotbarSlot\" is out of range");
 		}
 	}
 
@@ -206,26 +225,26 @@ class PlayerInventory extends BaseInventory{
 	 *
 	 * @return Item
 	 */
-	public function getItemInHand(){
+	public function getItemInHand() : Item{
 		return $this->getHotbarSlotItem($this->itemInHandIndex);
 	}
 
 	/**
 	 * Sets the item in the currently-held slot to the specified item.
+	 *
 	 * @param Item $item
 	 *
 	 * @return bool
 	 */
-	public function setItemInHand(Item $item){
+	public function setItemInHand(Item $item) : bool{
 		return $this->setItem($this->getHeldItemSlot(), $item);
 	}
 
 	/**
 	 * Returns the hotbar slot number currently held.
-	 *
 	 * @return int
 	 */
-	public function getHeldItemSlot(){
+	public function getHeldItemSlot() : int{
 		return $this->getHotbarSlotIndex($this->itemInHandIndex);
 	}
 
@@ -235,7 +254,7 @@ class PlayerInventory extends BaseInventory{
 	 *
 	 * @param int $slot
 	 */
-	public function setHeldItemSlot($slot){
+	public function setHeldItemSlot(int $slot){
 		if($slot >= -1 and $slot < $this->getSize()){
 			$this->setHotbarSlotIndex($this->getHeldItemIndex(), $slot);
 		}
@@ -268,7 +287,7 @@ class PlayerInventory extends BaseInventory{
 		}
 	}
 
-	public function onSlotChange($index, $before){
+	public function onSlotChange(int $index, Item $before, bool $send){
 		$holder = $this->getHolder();
 		if($holder instanceof Player and !$holder->spawned){
 			return;
@@ -279,7 +298,7 @@ class PlayerInventory extends BaseInventory{
 			$this->sendArmorSlot($index, $this->getHolder()->getViewers());
 		}else{
 			//Do not send armor by accident here.
-			parent::onSlotChange($index, $before);
+			parent::onSlotChange($index, $before, $send);
 		}
 	}
 
@@ -287,57 +306,51 @@ class PlayerInventory extends BaseInventory{
 	 * Returns the number of slots in the hotbar.
 	 * @return int
 	 */
-	public function getHotbarSize(){
+	public function getHotbarSize() : int{
 		return 9;
 	}
 
-	public function getArmorItem($index){
+	public function getArmorItem(int $index) : Item{
 		return $this->getItem($this->getSize() + $index);
 	}
 
-	public function setArmorItem($index, Item $item){
+	public function setArmorItem(int $index, Item $item) : bool{
 		return $this->setItem($this->getSize() + $index, $item);
 	}
 
-	public function getHelmet(){
+	public function getHelmet() : Item{
 		return $this->getItem($this->getSize());
 	}
 
-	public function getChestplate(){
+	public function getChestplate() : Item{
 		return $this->getItem($this->getSize() + 1);
 	}
 
-	public function getLeggings(){
+	public function getLeggings() : Item{
 		return $this->getItem($this->getSize() + 2);
 	}
 
-	public function getBoots(){
+	public function getBoots() : Item{
 		return $this->getItem($this->getSize() + 3);
 	}
 
-	public function setHelmet(Item $helmet){
+	public function setHelmet(Item $helmet) : bool{
 		return $this->setItem($this->getSize(), $helmet);
 	}
 
-	public function setChestplate(Item $chestplate){
+	public function setChestplate(Item $chestplate) : bool{
 		return $this->setItem($this->getSize() + 1, $chestplate);
 	}
 
-	public function setLeggings(Item $leggings){
+	public function setLeggings(Item $leggings) : bool{
 		return $this->setItem($this->getSize() + 2, $leggings);
 	}
 
-	public function setBoots(Item $boots){
+	public function setBoots(Item $boots) : bool{
 		return $this->setItem($this->getSize() + 3, $boots);
 	}
 
-	public function setItem(int $index, Item $item) : bool{
-		if($index < 0 or $index >= $this->size){
-			return false;
-		}elseif($item->getId() === 0 or $item->getCount() <= 0){
-			return $this->clear($index);
-		}
-
+	public function setItem(int $index, Item $item, bool $send = true) : bool{
 		if($index >= $this->getSize()){ //Armor change
 			Server::getInstance()->getPluginManager()->callEvent($ev = new EntityArmorChangeEvent($this->getHolder(), $this->getItem($index), $item, $index));
 			if($ev->isCancelled() and $this->getHolder() instanceof Human){
@@ -357,54 +370,25 @@ class PlayerInventory extends BaseInventory{
 
 		$old = $this->getItem($index);
 		$this->slots[$index] = clone $item;
-		$this->onSlotChange($index, $old);
+		$this->onSlotChange($index, $old, $send);
 
 		return true;
 	}
 
-	public function clear(int $index) : bool{
-		if(isset($this->slots[$index])){
-			$item = Item::get(Item::AIR, 0, 0);
-			$old = $this->slots[$index];
-			if($index >= $this->getSize() and $index < $this->size){ //Armor change
-				Server::getInstance()->getPluginManager()->callEvent($ev = new EntityArmorChangeEvent($this->getHolder(), $old, $item, $index));
-				if($ev->isCancelled()){
-					if($index >= $this->size){
-						$this->sendArmorSlot($index, $this->getViewers());
-					}else{
-						$this->sendSlot($index, $this->getViewers());
-					}
-					return false;
-				}
-				$item = $ev->getNewItem();
-			}else{
-				Server::getInstance()->getPluginManager()->callEvent($ev = new EntityInventoryChangeEvent($this->getHolder(), $old, $item, $index));
-				if($ev->isCancelled()){
-					if($index >= $this->size){
-						$this->sendArmorSlot($index, $this->getViewers());
-					}else{
-						$this->sendSlot($index, $this->getViewers());
-					}
-					return false;
-				}
-				$item = $ev->getNewItem();
-			}
-			if($item->getId() !== Item::AIR){
-				$this->slots[$index] = clone $item;
-			}else{
-				unset($this->slots[$index]);
-			}
+	public function clearAll(){
+		parent::clearAll();
 
-			$this->onSlotChange($index, $old);
+		for($i = $this->getSize(), $m = $i + 4; $i < $m; ++$i){
+			$this->clear($i, false);
 		}
 
-		return true;
+		$this->sendArmorContents($this->getViewers());
 	}
 
 	/**
 	 * @return Item[]
 	 */
-	public function getArmorContents(){
+	public function getArmorContents() : array{
 		$armor = [];
 
 		for($i = 0; $i < 4; ++$i){
@@ -414,13 +398,6 @@ class PlayerInventory extends BaseInventory{
 		return $armor;
 	}
 
-	public function clearAll(){
-		$limit = $this->getSize() + 4;
-		for($index = 0; $index < $limit; ++$index){
-			$this->clear($index);
-		}
-	}
-
 	/**
 	 * @param Player|Player[] $target
 	 */
@@ -457,12 +434,10 @@ class PlayerInventory extends BaseInventory{
 				$items[$i] = Item::get(Item::AIR, 0, 0);
 			}
 
-			if($items[$i]->getId() === Item::AIR){
-				$this->clear($this->getSize() + $i);
-			}else{
-				$this->setItem($this->getSize() + $i, $items[$i]);
-			}
+			$this->setItem($this->getSize() + $i, $items[$i], false);
 		}
+
+		$this->sendArmorContents($this->getViewers());
 	}
 
 
@@ -470,7 +445,7 @@ class PlayerInventory extends BaseInventory{
 	 * @param int             $index
 	 * @param Player|Player[] $target
 	 */
-	public function sendArmorSlot($index, $target){
+	public function sendArmorSlot(int $index, $target){
 		if($target instanceof Player){
 			$target = [$target];
 		}
@@ -520,11 +495,7 @@ class PlayerInventory extends BaseInventory{
 			$player->dataPacket(clone $pk);
 
 			if($player === $this->getHolder()){
-				$pk = new PlayerHotbarPacket();
-				$pk->slots = array_map(function(int $i){ return $i + $this->getHotbarSize(); }, $this->hotbar);
-				$pk->selectedSlot = $this->getHeldItemIndex();
-				$pk->windowId = ContainerIds::INVENTORY;
-				$player->dataPacket($pk);
+				$this->sendHotbar();
 			}
 		}
 	}
@@ -545,7 +516,7 @@ class PlayerInventory extends BaseInventory{
 	 * @param int             $index
 	 * @param Player|Player[] $target
 	 */
-	public function sendSlot($index, $target){
+	public function sendSlot(int $index, $target){
 		if($target instanceof Player){
 			$target = [$target];
 		}
@@ -571,10 +542,11 @@ class PlayerInventory extends BaseInventory{
 	}
 
 	/**
+	 * This override is here for documentation and code completion purposes only.
 	 * @return Human|Player
 	 */
 	public function getHolder(){
-		return parent::getHolder();
+		return $this->holder;
 	}
 
 }
diff --git a/src/pocketmine/item/Item.php b/src/pocketmine/item/Item.php
index c073a6e2e..a3cba941c 100644
--- a/src/pocketmine/item/Item.php
+++ b/src/pocketmine/item/Item.php
@@ -828,6 +828,10 @@ class Item implements ItemIds, \JsonSerializable{
 		$this->count = $count;
 	}
 
+	public function isNull() : bool{
+		return $this->count <= 0 or $this->id === Item::AIR;
+	}
+
 	/**
 	 * Returns the name of the item, or the custom name if it is set.
 	 * @return string