pocketmine\network\protocol\BatchPacket::encode PHP Method

    public function encode()
    {
        $this->reset();
        $this->putString($this->payload);
    }

 public function broadcastPacketsCallback($data, array $identifiers)
 {
     $pk = new BatchPacket();
     $pk->payload = $data;
     $pk->encode();
     $pk->isEncoded = true;
     foreach ($identifiers as $i) {
         if (isset($this->players[$i])) {
             $this->players[$i]->dataPacket($pk);
         }
     }
 }