pocketmine\event\player\PlayerDropItemEvent::getItem PHP Method

    public function getItem()
    {
        return $this->drop;
    }

 public function onDropItem(PlayerDropItemEvent $event)
 {
     $item = $event->getItem();
     if ($item->getId() === self::GRENADE_ID) {
         $event->setCancelled();
     } elseif ($item->getId() === self::GUN_ID) {
         $event->setCancelled();
     }
 }