static function simpleXmlToArrayHelper(&$res, &$key, &$value, &$children)
  {
    if (isset($res[$key])) {
      if (is_string($res[$key]) || (is_array($res[$key]) && is_assoc($res[$key]))) {
        $res[$key] = array($res[$key]);
      }
      $res[$key][] = CPS_Response::simpleXmlToArray($value);
    } else {
      $res[$key] = CPS_Response::simpleXmlToArray($value);
    }
    $children = true;
  }