Use of HTTP_REFERER to delete session data

gistfile1.txt

Use of $_SERVER['HTTP_REFERER'];

I assume in a.php

     <?php
        session_start();
        $_SESSION['hello'] = "Your content here";
     ?>

In b.php you want to show your session data and you are also checking what is the previous page
    
    <?php
       session_start();
       $previousUrl = parse_url($_SERVER['HTTP_REFERER'], PHP_URL_PATH);
       if($previousUrl == '/phpTest/php/c.php') {
          unset($_SESSION['hello']);
      }
      echo $_SESSION['hello'];
    ?>
And in c.php you might have a back button or there is also browser back button

    <p>Show your confirmation</p>
    <a href="b.php">Back or back from browser button<a>