private static function cssMatcher($matches) {

        $chr = $matches[0];

        if(1 === strlen($chr)) {
            $ord = ord($chr);
        }
        else {
            
            $chr = static :: convert($chr, 'UTF-8', 'UTF-32BE');
            $ord = hexdec(bin2hex($chr));
        }

        return sprintf('\\%X ', $ord);
    }