How can I disable the back browser button after user press logout and destroy session?

Question

I am having trouble with session_destroy().

When the User press Log out it have to destroy the session. I wrote the following code:

Logout.php

<?php
    session_start();
    session_destroy();
    header("location: LoginViewController.php");
?>

After pressing log out, when I press the browser back button it is showing my previous Logined user page and session username in Login.php page

Login.php

<?php
    session_start();
    $_SESSION['user']=  $_GET['username'];
    echo '"<div style="background:white; text-align:right"> Login as:'.$_SESSION['user'].'</div>"';
    echo '<a href="Logout.php" style="text-align:right">Logout</a>';

LoginViewController.php

<?php
    header("Cache-Control: no-store, no-cache, must-revalidate, max-age=0");
    header("Expires: Sat, 26 Jul 1997 05:00:00 GMT");

    $Username = $_POST['uname'];
    $Password = $_POST['pwd'];
    $User_Type=$_POST['type'];

    If (!(empty($Username) && empty($Password) && empty($User_Type))){
        $model = new UsersModel();
        $rowsCount = $model->checkUser($Username,$Password,$User_Type);

        if ($rowsCount!=0){
            header("location:login.php?username=".$_POST['uname']."");  
        } else {
            echo '<script type="text/javascript">alert("Enter username and password correctly");
            window.location.href="LoginViewController.php";</script>';
        }
    }

I don't know why it is working like that.

Please help me to find out where I commit mistake.

I want to disable that browser back button after logout.

Answer 1

login.php page :

<?php 
    if (isset($_POST['uname'], $_POST['pwd'], $_POST['type'])) {
        $Username = $_POST['uname'];
        $Password = $_POST['pwd'];
        $User_Type=$_POST['type'];
        if (!(empty($Username) || empty($Password) || empty($User_Type))) 
        {
             $model = new UsersModel();
             $rowsCount = $model->checkUser($Username,$Password,$User_Type);
             if ($rowsCount!=0)
             {
                  $_SESSION['user'] = $Username;
                  header("Location:LoginViewController.php");

             } else {
                  echo 'Bad user';
             }
        } else {
             echo 'Please, fill all inputs';
        }
    } else {
        echo 'Bad form sent';
    }
?>
<form name="f1" method="POST" action="" >
    // inputs
</form>

LoginViewController.php :

<?php
header("Cache-Control: no-store, no-cache, must-revalidate, max-age=0");
header("Expires: Sat, 26 Jul 1997 05:00:00 GMT");

if (!isset($_SESSION['user'])) {
    header('Location: login.php');
    exit();
}
echo 'You have successfully logged as '.$_SESSION['user']
?>

And add the headers to force the browser to revalidate the pages :

logout.php :

<?php 
session_start();
session_destroy();
$_SESSION = array();
header("location: login.php");
?>

Answer 2

This is caused by the browser cache that is keeping details in the page, if you refresh the page or you move any further in your private area you will be prompted to login page and you will not be able to see anything, assuming that your login check system is correctly configured.

You can otherwise force the browser to not cache the page and have a new request to the server for the page

header("Cache-Control: private, must-revalidate, max-age=0");
header("Pragma: no-cache");
header("Expires: Fri, 4 Jun 2010 12:00:00 GMT");