Logout problem

Hi, I have problem I copied the function logout from the sitecontroller to my admincontroller




  public function actionLogout()

    {

        Yii::$app->user->logout();


        return $this->goHome(); 

    }






but after it logout and clicking the back button, still I can get back to the previous page…but why is it the logout is working in the sitecontroller…in my admincontroller it’s not working





<?php




namespace app\controllers;




use app\models\User;

use Yii;




class AdminsiteController extends \yii\web\Controller

{


    public $layout = 'adminmain';








    public function actionIndex()

    {


       if(isset(Yii::$app->session->id)){

           return $this->render('index');

       }


        return $this->redirect(array('site/index'));


    }


    public function actionTest(){

        return $this->render('test');

    }


    public function actionLogout()

    {

        Yii::$app->user->logout();


        return $this->goHome();

    }


}







can someone help me please,why is it that the document will not expired after I log-out if I am in my admin page,but if I am in the yii default basic dashboard it will expire the document after i log-out If I click the back button in broswer I could not go back to the previous page…Is there something wrong in my adminpage ? but I just followed how yii created the log out…by invoking this




  Yii::$app->user->logout();