pocketmine\nbt\NBT::put PHP Method

    public function put($v)
    {
        $this->buffer .= $v;
    }

 public function write(NBT $nbt)
 {
     $nbt->putInt(count($this->value));
     $nbt->put(pack($nbt->endianness === NBT::LITTLE_ENDIAN ? "V*" : "N*", ...$this->value));
 }