Sluggify in PHP

slug.php

<?php
class Modify {
    private static   $instance = NULL;
    protected static $mbstring = NULL;
    protected static $iconv = NULL;
    protected static $characterset = NULL;

    /*
    protected static $diacritics  = array(
        'À'=>'A','Á'=>'A','Â'=>'A','Ã'=>'A','Å'=>'A','Ä'=>'A','Æ'=>'AE',
        'à'=>'a','á'=>'a','â'=>'a','ã'=>'a','å'=>'a','ä'=>'a','æ'=>'ae',
        'Þ'=>'B','þ'=>'b','Č'=>'C','Ć'=>'C','Ç'=>'C','č'=>'c','ć'=>'c',
        'ç'=>'c','Ď'=>'D','ð'=>'d','ď'=>'d','Đ'=>'Dj','đ'=>'dj','È'=>'E',
        'É'=>'E','Ê'=>'E','Ë'=>'E','è'=>'e','é'=>'e','ê'=>'e','ë'=>'e',
        'Ì'=>'I','Í'=>'I','Î'=>'I','Ï'=>'I','ì'=>'i','í'=>'i','î'=>'i',
        'ï'=>'i','Ľ'=>'L','ľ'=>'l','Ñ'=>'N','Ň'=>'N','ñ'=>'n','ň'=>'n',
        'Ò'=>'O','Ó'=>'O','Ô'=>'O','Õ'=>'O','Ø'=>'O','Ö'=>'O','Œ'=>'OE',
        'ð'=>'o','ò'=>'o','ó'=>'o','ô'=>'o','õ'=>'o','ö'=>'o','œ'=>'oe',
        'ø'=>'o','Ŕ'=>'R','Ř'=>'R','ŕ'=>'r','ř'=>'r','Š'=>'S','š'=>'s',
        'ß'=>'ss','Ť'=>'T','ť'=>'t','Ù'=>'U','Ú'=>'U','Û'=>'U','Ü'=>'U',
        'Ů'=>'U','ù'=>'u','ú'=>'u','û'=>'u','ü'=>'u','ů'=>'u','Ý'=>'Y',
        'Ÿ'=>'Y','ý'=>'y','ý'=>'y','ÿ'=>'y','Ž'=>'Z','ž'=>'z'
    );
    */

    private function __construct() {
        self::$mbstring     = extension_loaded('mbstring');
        self::$iconv        = extension_loaded('iconv');
        self::$characterset = ini_get('default_charset');

        if(self::$mbstring !== true) {
            throw new \Exception('Extension "mbstring" not loaded');
        }

        if(self::$iconv !== true) {
            throw new \Exception('Extension "iconv" not loaded');
        }

        if(empty(self::$characterset)) {
            throw new \Exception('no "default_charset" set');
        }
    }

    public static function transliterate($value, $characterset = NULL) {
        if(self::$instance === NULL) {
            self::$instance = new self();
        }

        if($characterset === NULL) {
            $characterset = self::$characterset;
        }

        return iconv(mb_detect_encoding($value, NULL, true), $characterset . '//IGNORE//TRANSLIT', trim($value));
    }

    public static function sluggify($value) {
        if(self::$instance === NULL) {
            self::$instance = new self();
        }

        //return trim(strtolower(preg_replace('/([^\w]|-)+/', '-', trim(strtr(str_replace('\'', '', trim($value)), self::$diacritics)))));

        return strtolower(preg_replace('/([^\w0-9_]|-)+/', '-', iconv(mb_detect_encoding($value, 'auto', true), 'ASCII//TRANSLIT//IGNORE', trim($value))));
    }
}
?>

usage.php

<?php
// include/require/load slup.php
ini_set('default_charset', 'utf-8');
echo Modify::sluggify('Gnarf äüö? hützli pötzli')  .chr(10) . '<br />';
die();
?>