public static function has(string $name, ?string $syntax = null)
  {
    if (isset($_SESSION['application']['with'][$name])) {
      $_SESSION['application']['flash']['used'] = true;

      $name = $_SESSION['application']['with'][$name];

      return $syntax ? str_replace(':message', $name, $syntax) : true;
    }

    return isset(Variable::$data[$name]) ? ($syntax ? str_replace(':message', Variable::$data[$name], $syntax) : true) : false;
  }