Slugify

function slugify($string){
    $string = strtolower(trim($string));
    $string = str_replace(array('å', 'ä', 'ö'), array('a', 'a', 'o'), $string);
    $string = preg_replace('/[^a-z0-9-]/', '-', $string);
    $string = preg_replace('/-+/', "-", $string);
    return $string;
}

UTF-8
 function slugify($string){
            $string = mb_strtolower(trim($string),'UTF-8');
            $string = str_replace(array('å', 'ä', 'ö'), array('a', 'a', 'o'), $string);
            $string = preg_replace('/[^a-z0-9-]/', '-', $string);
            $string = preg_replace('/-+/', "-", $string);
            return $string;
  }