<?php

class MessagePackCustom extends MessagePack\Packer 
{
  public function __construct()
  {
      parent::__construct(MessagePack\PackOptions::FORCE_STR);
  }

  public function packStr($str)
  {
      $length = \strlen($str);

      if ($length < 32) {
          return \chr(0xa0 | $length).$str;
      }
      if ($length <= 0xffff) {
          return "\xda".\chr($length >> 8).\chr($length).$str;
      }

      return \pack('CN', 0xdb, $length).$str;
  }
}