function slug($text){

  // replace non letter or digits by -

  $text = preg_replace(~[^pLd]+~u, -, $text);

  // transliterate

  $text = iconv(utf-8, us-ascii//TRANSLIT, $text);

  // remove unwanted characters

  $text = preg_replace(~[^-w]+~, , $text);

  // trim

  $text = trim($text, -);

  // remove duplicate -

  $text = preg_replace(~-+~, -, $text);

  // lowercase

  $text = strtolower($text);

  if (empty($text)) {

    return n-a;

  }

  return $text;

}