diff --git a/src/pocketmine/entity/Human.php b/src/pocketmine/entity/Human.php
index 240d51b04..74d099df0 100644
--- a/src/pocketmine/entity/Human.php
+++ b/src/pocketmine/entity/Human.php
@@ -618,8 +618,8 @@ class Human extends Creature implements ProjectileSource, InventoryHolder{
 
 		$inventoryTag = $nbt->getListTag("Inventory");
 		if($inventoryTag !== null){
-			$armorListener = $this->armorInventory->getSlotChangeListener();
-			$this->armorInventory->setSlotChangeListener(null);
+			$armorListeners = $this->armorInventory->getChangeListeners();
+			$this->armorInventory->removeChangeListeners(...$armorListeners);
 
 			/** @var CompoundTag $item */
 			foreach($inventoryTag as $i => $item){
@@ -633,7 +633,7 @@ class Human extends Creature implements ProjectileSource, InventoryHolder{
 				}
 			}
 
-			$this->armorInventory->setSlotChangeListener($armorListener);
+			$this->armorInventory->addChangeListeners(...$armorListeners);
 		}
 
 		$enderChestInventoryTag = $nbt->getListTag("EnderChestInventory");
diff --git a/src/pocketmine/inventory/BaseInventory.php b/src/pocketmine/inventory/BaseInventory.php
index bb1b52ad0..9be938cbf 100644
--- a/src/pocketmine/inventory/BaseInventory.php
+++ b/src/pocketmine/inventory/BaseInventory.php
@@ -27,7 +27,6 @@ use pocketmine\event\inventory\InventoryOpenEvent;
 use pocketmine\item\Item;
 use pocketmine\item\ItemFactory;
 use pocketmine\Player;
-use pocketmine\utils\Utils;
 use function array_slice;
 use function count;
 use function max;
@@ -42,8 +41,8 @@ abstract class BaseInventory implements Inventory{
 	protected $slots = [];
 	/** @var Player[] */
 	protected $viewers = [];
-	/** @var \Closure */
-	protected $slotChangeListener;
+	/** @var InventoryChangeListener[] */
+	protected $listeners = [];
 
 	/**
 	 * @param int    $size
@@ -121,6 +120,10 @@ abstract class BaseInventory implements Inventory{
 			}
 		}
 
+		foreach($this->listeners as $listener){
+			$listener->onContentChange($this);
+		}
+
 		if($send){
 			$this->sendContents($this->getViewers());
 		}
@@ -138,10 +141,6 @@ abstract class BaseInventory implements Inventory{
 		$this->slots[$index] = $item->isNull() ? null : $item;
 		$this->onSlotChange($index, $oldItem, $send);
 
-		if($this->slotChangeListener !== null){
-			($this->slotChangeListener)($this, $index);
-		}
-
 		return true;
 	}
 
@@ -331,13 +330,7 @@ abstract class BaseInventory implements Inventory{
 	}
 
 	public function clearAll(bool $send = true) : void{
-		for($i = 0, $size = $this->getSize(); $i < $size; ++$i){
-			$this->clear($i, false);
-		}
-
-		if($send){
-			$this->sendContents($this->getViewers());
-		}
+		$this->setContents([], $send);
 	}
 
 	public function swap(int $slot1, int $slot2) : void{
@@ -394,6 +387,9 @@ abstract class BaseInventory implements Inventory{
 	}
 
 	protected function onSlotChange(int $index, Item $before, bool $send) : void{
+		foreach($this->listeners as $listener){
+			$listener->onSlotChange($this, $index);
+		}
 		if($send){
 			$this->sendSlot($index, $this->getViewers());
 		}
@@ -430,14 +426,19 @@ abstract class BaseInventory implements Inventory{
 		return $slot >= 0 and $slot < $this->slots->getSize();
 	}
 
-	public function getSlotChangeListener() : ?\Closure{
-		return $this->slotChangeListener;
+	public function addChangeListeners(InventoryChangeListener ...$listeners) : void{
+		foreach($listeners as $listener){
+			$this->listeners[spl_object_id($listener)] = $listener;
+		}
 	}
 
-	public function setSlotChangeListener(?\Closure $eventProcessor) : void{
-		if($eventProcessor !== null){
-			Utils::validateCallableSignature(function(Inventory $inventory, int $slot) : void{}, $eventProcessor);
+	public function removeChangeListeners(InventoryChangeListener ...$listeners) : void{
+		foreach($listeners as $listener){
+			unset($this->listeners[spl_object_id($listener)]);
 		}
-		$this->slotChangeListener = $eventProcessor;
+	}
+
+	public function getChangeListeners() : array{
+		return $this->listeners;
 	}
 }
diff --git a/src/pocketmine/inventory/CallbackInventoryChangeListener.php b/src/pocketmine/inventory/CallbackInventoryChangeListener.php
new file mode 100644
index 000000000..b27499740
--- /dev/null
+++ b/src/pocketmine/inventory/CallbackInventoryChangeListener.php
@@ -0,0 +1,65 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+*/
+
+declare(strict_types=1);
+
+namespace pocketmine\inventory;
+
+use pocketmine\utils\Utils;
+
+class CallbackInventoryChangeListener implements InventoryChangeListener{
+
+	/** @var \Closure|null */
+	private $onSlotChangeCallback;
+	/** @var \Closure|null */
+	private $onContentChangeCallback;
+
+	public function __construct(?\Closure $onSlotChange, ?\Closure $onContentChange){
+		if($onSlotChange !== null){
+			Utils::validateCallableSignature(function(Inventory	$inventory, int $slot){}, $onSlotChange);
+		}
+		if($onContentChange !== null){
+			Utils::validateCallableSignature(function(Inventory $inventory){}, $onContentChange);
+		}
+
+		$this->onSlotChangeCallback = $onSlotChange;
+		$this->onContentChangeCallback = $onContentChange;
+	}
+
+	public static function onAnyChange(\Closure $onChange) : self{
+		return new self(
+			static function(Inventory $inventory, int $unused) use($onChange) : void{
+				$onChange($inventory);
+			},
+			static function(Inventory $inventory) use($onChange) : void{
+				$onChange($inventory);
+			}
+		);
+	}
+
+	public function onSlotChange(Inventory $inventory, int $slot) : void{
+		($this->onSlotChangeCallback)($inventory, $slot);
+	}
+
+	public function onContentChange(Inventory $inventory) : void{
+		($this->onContentChangeCallback)($inventory);
+	}
+}
diff --git a/src/pocketmine/inventory/Inventory.php b/src/pocketmine/inventory/Inventory.php
index c0fba1d2b..a27a8525c 100644
--- a/src/pocketmine/inventory/Inventory.php
+++ b/src/pocketmine/inventory/Inventory.php
@@ -231,12 +231,17 @@ interface Inventory{
 	public function slotExists(int $slot) : bool;
 
 	/**
-	 * @return null|\Closure
+	 * @param InventoryChangeListener ...$listeners
 	 */
-	public function getSlotChangeListener() : ?\Closure;
+	public function addChangeListeners(InventoryChangeListener ...$listeners) : void;
 
 	/**
-	 * @param \Closure|null $eventProcessor
+	 * @param InventoryChangeListener ...$listeners
 	 */
-	public function setSlotChangeListener(?\Closure $eventProcessor) : void;
+	public function removeChangeListeners(InventoryChangeListener ...$listeners) : void;
+
+	/**
+	 * @return InventoryChangeListener[]
+	 */
+	public function getChangeListeners() : array;
 }
diff --git a/src/pocketmine/inventory/InventoryChangeListener.php b/src/pocketmine/inventory/InventoryChangeListener.php
new file mode 100644
index 000000000..d13edf7f0
--- /dev/null
+++ b/src/pocketmine/inventory/InventoryChangeListener.php
@@ -0,0 +1,38 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+*/
+
+declare(strict_types=1);
+
+namespace pocketmine\inventory;
+
+/**
+ * Classes implementing this interface can be injected into inventories to receive notifications when content changes
+ * occur.
+ * @see CallbackInventoryChangeListener for a closure-based listener
+ * @see Inventory::addChangeListeners()
+ * @see Inventory::removeChangeListeners()
+ */
+interface InventoryChangeListener{
+
+	public function onSlotChange(Inventory $inventory, int $slot) : void;
+
+	public function onContentChange(Inventory $inventory) : void;
+}
diff --git a/src/pocketmine/tile/ContainerTrait.php b/src/pocketmine/tile/ContainerTrait.php
index 1ef2737d1..28cc6b04e 100644
--- a/src/pocketmine/tile/ContainerTrait.php
+++ b/src/pocketmine/tile/ContainerTrait.php
@@ -48,14 +48,14 @@ trait ContainerTrait{
 			$inventoryTag = $tag->getListTag(Container::TAG_ITEMS);
 
 			$inventory = $this->getRealInventory();
-			$slotChangeListener = $inventory->getSlotChangeListener();
-			$inventory->setSlotChangeListener(null); //prevent any events being fired by initialization
+			$listeners = $inventory->getChangeListeners();
+			$inventory->removeChangeListeners(...$listeners); //prevent any events being fired by initialization
 			$inventory->clearAll();
 			/** @var CompoundTag $itemNBT */
 			foreach($inventoryTag as $itemNBT){
 				$inventory->setItem($itemNBT->getByte("Slot"), Item::nbtDeserialize($itemNBT));
 			}
-			$inventory->setSlotChangeListener($slotChangeListener);
+			$inventory->addChangeListeners(...$listeners);
 		}
 
 		if($tag->hasTag(Container::TAG_LOCK, StringTag::class)){
diff --git a/src/pocketmine/tile/Furnace.php b/src/pocketmine/tile/Furnace.php
index 26ce225ab..ad9337139 100644
--- a/src/pocketmine/tile/Furnace.php
+++ b/src/pocketmine/tile/Furnace.php
@@ -26,6 +26,7 @@ namespace pocketmine\tile;
 use pocketmine\block\Furnace as BlockFurnace;
 use pocketmine\event\inventory\FurnaceBurnEvent;
 use pocketmine\event\inventory\FurnaceSmeltEvent;
+use pocketmine\inventory\CallbackInventoryChangeListener;
 use pocketmine\inventory\FurnaceInventory;
 use pocketmine\inventory\FurnaceRecipe;
 use pocketmine\inventory\Inventory;
@@ -60,9 +61,11 @@ class Furnace extends Spawnable implements InventoryHolder, Container, Nameable{
 
 	public function __construct(World $world, Vector3 $pos){
 		$this->inventory = new FurnaceInventory($this);
-		$this->inventory->setSlotChangeListener(function(Inventory $inventory, int $slot) : void{
-			$this->scheduleUpdate();
-		});
+		$this->inventory->addChangeListeners(CallbackInventoryChangeListener::onAnyChange(
+			function(Inventory $unused) : void{
+				$this->scheduleUpdate();
+			})
+		);
 
 		parent::__construct($world, $pos);
 	}