How to pass session variables when header redirects? loosing session variables during the process of redirection

Question

session varibales

<?php session_start(); 
error_reporting(-1);
if (!isset($_SESSION)){
}
$total_amt=$_POST['total_amt'];
$total_seats=$_POST['total_seats'];
$seat=$_POST['seat'];
$boarding_point=$_POST['boarding_point'];
$submit=$_POST['chksbmt'];
$_SESSION['total_amt']=$total_amt;
$_SESSION['total_seats']=$total_seats;
$_SESSION['seat']=$seat;
$_SESSION['boarding_point']=$boarding_point;
$_SESSION['chksbmt']=$submit;
?>

<?php
$serial_no = 1;
$total_seats = $_SESSION['total_seats']; 
$seats=explode(',', rtrim($total_seats, ","));
foreach ($seats as $seat) { ?>
<tr>
<td style="text-align:center;"> <?php echo $serial_no++; ?></td>
  <td style="text-align:center;"><?php echo $seat; ?> </td>

& so on ..

login div

<ul class="top">
         <li><a href="registration.php" class="about">Registration</a>
        </li>
       <?php if(!isset($_SESSION['login_user'])) { ?>
        <li class="hover"><a href="#" onClick="revealModal('modalPage')">Login</a>
        </li>
         <?php } else {?>
        <li class="hover"><a href="logout.php">Logout</a></li>
    <div style="color:#00CC66;">Welcome <?php echo $_SESSION['login_user'];     ?></div>
         <?php } ?>
              </ul>

logout.php

<?php session_start();
session_destroy(); 
header('Location:'.$_SERVER['HTTP_REFERER']);  
exit;  
?>  

When m logging out from my page, it has to be redirected & in this process i m loosing my session variables. Is that any process to keep the variables constant after the redirection .. After the page redirection m getting undefined index error.. Any help .. ?? Thank you in advance

Answer 1

You're destroying whole session on logout page. While you just need to unset the relevant session key.

Something like,

session_start();
unset($_SESSION['login_user']); //session_destroy(); 
header('Location:'.$_SERVER['HTTP_REFERER']);  
exit;  

Answer 2

instead of using session_destroy();
you should use unset($_SESSION['login_user']);

It will change the value of the variable in the session to null and you will not lose your variable. session_destroy() destroys the session completely and then you have no way to access that variable.
You can check the difference between them using var_dump
eg:- session_destroy(); var_dump($_SESSION['login_user']);
and
unset($_SESSION['login_user']); var_dump($_SESSION['login_user']);
AND in your code

if (!isset($_SESSION)){
}

you should not keep it blank. I think you forgot to include the following code inside this block