NetworkBinaryStream error

I'm making an npc plugin, and gave this bug here:

how to resolve the error?
code:

PHP:

public function spawnTo(Player $player) : void {
        if($player !== $this and !isset($this->hasSpawned[$player->getLoaderId()])){
            $this->hasSpawned[$player->getLoaderId()] = $player;
        }
        $pk = new AddPlayerPacket();
        $pk->uuid = $this->getUniqueId();
        $pk->entityUniqueId = 0;
        $pk->entityRuntimeId = 0;
        $pk->position = new Vector3($this->x, $this->y, $this->z);
        $pk->motion = $this->motion;
        $pk->pitch = $this->pitch;
        $pk->username = "";
        $pk->platformChatId = "";
        $pk->buildPlatform = DeviceOS::ANDROID;
        $pk->yaw = $this->yaw;
        $pk->item = new ItemStackWrapper(0, Item::get(0,0,0));
        $pk->metadata = [
            Entity::DATA_FLAGS => [
                Entity::DATA_TYPE_LONG, 1 << Entity::DATA_FLAG_ALWAYS_SHOW_NAMETAG
                ^ 1 << Entity::DATA_FLAG_CAN_SHOW_NAMETAG
            ],
            Entity::DATA_NAMETAG => [Entity::DATA_TYPE_STRING, $this->getMetadata(4)],
            Entity::DATA_LEAD_HOLDER_EID => [Entity::DATA_TYPE_LONG, -1],
            Entity::DATA_SCALE => [Entity::DATA_TYPE_FLOAT, 0.000001]
        ];
        $player->dataPacket($pk);
        $this->inventory->sendArmorContents($player);
    }

 

PHP:

Entity::DATA_NAMETAG => [Entity::DATA_TYPE_STRING, $this->getMetadata(4)],


?