public static function set($language = null)
    {
        self::$messages = array();
        $language = $language ?: self::$config['language'];
        $filename = Atomik::findFile("$language.php", Atomik::path(self::$config['dir']));
        if ($filename === false) {
            throw new AtomikException("Language '$language' does not exists");
        }
        
        $messages = include $filename;
        if (is_array($messages)) {
            self::$messages = array_merge(self::$messages, $messages);
        }
        
        Atomik::set('app.language', $language);
        self::$config['language'] = $language;
        if (isset($_SESSION)) {
            $_SESSION['__LANG'] = $language;
        }
    }