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 duplicated - symbols
    $text = preg_replace('~-+~', '-', $text);

    // lowercase
    $text = strtolower($text);

    if (empty($text)) {
      return 'n-a';
    }

    return $text;
}

function filterSlug($ax, $bx){
    if(isset($_POST[$ax]) && $_POST[$ax] != ''){
        $ax = slug($ax);
    } else {
        $ax = slug($bx);
    }
    }

filterSlug($postSlug, $postTitle);

if(isset($_POST['postSlug']) && $_POST['postSlug'] != ''){
                    $postSlug = slug($postSlug);
                } else {
                    $postSlug = slug($postTitle);
                }