pocketmine\entity\Entity::despawnFrom PHP Method

    public function despawnFrom(Player $player)
    {
        if (isset($this->hasSpawned[$player->getLoaderId()])) {
            $pk = new RemoveEntityPacket();
            $pk->eid = $this->getId();
            $player->dataPacket($pk);
            unset($this->hasSpawned[$player->getLoaderId()]);
        }
    }