Session::isConcurrentSessionExists PHP Метод

    public static function isConcurrentSessionExists()
    {
        $session_id = session_id();
        $userId = Session::get('user_id');
        if (isset($userId) && isset($session_id)) {
            $database = DatabaseFactory::getFactory()->getConnection();
            $sql = "SELECT session_id FROM users WHERE user_id = :user_id LIMIT 1";
            $query = $database->prepare($sql);
            $query->execute(array(":user_id" => $userId));
            $result = $query->fetch();
            $userSessionId = !empty($result) ? $result->session_id : null;
            return $session_id !== $userSessionId;
        }
        return false;
    }

 /**
  * Detects if there is concurrent session (i.e. another user logged in with the same current user credentials),
  * If so, then logout.
  */
 public static function checkSessionConcurrency()
 {
     if (Session::userIsLoggedIn()) {
         if (Session::isConcurrentSessionExists()) {
             LoginModel::logout();
             Redirect::home();
             exit;
         }
     }
 }