Not working authentication

I use standard demo example authentication, in basic version Yii2.

Server PHP :session.gc_maxlifetime = 1440

1. I open -


http://localhost/basic/web/index.php?r=site/login

Yii::$app->user->isGuest === 1

2. I write login and password: admin/admin


Yii::$app->user->login($this->getUser(), 60);

Yii::$app->user->isGuest === NULL

3. I close browser and web-server

4. I wait 3 day

5. I open browser, web-server and open site.

6. Yii::$app->user->isGuest === Null <------ Why?