pocketmine\inventory\BaseInventory::onSlotChange PHP Method

    public function onSlotChange($index, $before, $send)
    {
        if ($send) {
            $this->sendSlot($index, $this->getViewers());
        }
    }

 public function onSlotChange($index, $before, $source = null)
 {
     parent::onSlotChange($index, $before, $source);
     if ($index >= $this->getSize()) {
         $this->sendArmorContents($this->getHolder()->getViewers());
     }
 }