urldecode и кодировки

/**
 * Improved variant of urldecode.
 * Properly decodes both UTF-8 and ISO-8859-1 encoded URIs.
 *
 * @param string $str encoded string
 * @return string decoded string
 */
private function urldecode($str)
{
    $str = urldecode($str);
 
    // is it UTF-8?
    // http://w3.org/International/questions/qa-forms-utf-8.html
    if(preg_match('%^(?:
       [\x09\x0A\x0D\x20-\x7E]            # ASCII
     | [\xC2-\xDF][\x80-\xBF]             # non-overlong 2-byte
     | \xE0[\xA0-\xBF][\x80-\xBF]         # excluding overlongs
     | [\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}  # straight 3-byte
     | \xED[\x80-\x9F][\x80-\xBF]         # excluding surrogates
     | \xF0[\x90-\xBF][\x80-\xBF]{2}      # planes 1-3
     | [\xF1-\xF3][\x80-\xBF]{3}          # planes 4-15
     | \xF4[\x80-\x8F][\x80-\xBF]{2}      # plane 16
    )*$%xs', $str))
    {
        return $str;
    }
    else
    {
        return utf8_encode($str);
    }
}