make __() faster

gistfile1.php

class myI18N extends sfI18N
{
  public function __($string, $args = array(), $catalogue = 'messages')
  {
    $string = (string) $string;

    if ($this->cache)
    {
      // the arguments stuff should probably be removed as this will cause
      // a lot of cache entries
      $argsStr = '';
      foreach ($args as $arg => $value)
      {
        $argsStr .= $arg.(string)$value;
      }
      $key = 'i18n_trans:'.md5($this->getCulture().$catalogue.$string.$argsStr);

      if ($translation = $this->cache->get($key))
      {
        return $translation;
      }
    }

    $translation = parent::__($string, $args, $catalogue);

    if (!empty($key))
    {
      $this->cache->set($key, $translation);
    }

    return $translation;
  }
}