public function filter($value)
    {
        $whiteSpace = $this->allowWhiteSpace ? '\s' : '';
        if (!self::$_unicodeEnabled) {
            // POSIX named classes are not supported, use alternative a-zA-Z0-9 match
            $pattern = '/[^a-zA-Z0-9' . $whiteSpace . ']/';
        } else {
            // Unicode safe filter for the value

            if(extension_loaded('mbstring')){
                $pattern = '/[^[:alnum:]' . $whiteSpace . ']/u';
            }else{
                $pattern = '/[^\p{L}\p{N}' . $whiteSpace . ']/u';
            }
        }

        return preg_replace($pattern, '', (string) $value);
    }