I'm encountering a (apparently common) problem with browser caches, and my secure pages being accessible via the back button (after user logout.)

Here is my logout.php

```
<?php
    // 1. Find the session 
    session_start();

    // 2. Unset all the session variables
    $_SESSION = array();

    // 3. Destroy the session cookie
    if(isset($_COOKIE[session_name()])) {
        setcookie(session_name(), '', time()-42000, '/');
    }

    // 4. Destroy the session
    session_destroy();

    redirect_to('index.php?logout=1');
?>

```

This successfully logs out users on IE7, IE8, Chrome and Firefox--but in Safari, I'm able to press the back button (immediately after logging out) and still see the secure content. If I refresh the secure page, it boots me to the login screen (as it should.)

I've tried using:

```
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Expires" CONTENT="-1">

```

...but it has no effect. Can anyone offer any advice? I've found [this article](http://www.mnot.net/cache_docs/) on browser caching, but I have yet to find an answer within it... although I did find:

```
<?php
 Header("Cache-Control: must-revalidate");

 $offset = 60 * 60 * 24 * 3;
 $ExpStr = "Expires: " . gmdate("D, d M Y H:i:s", time() + $offset) . " GMT";
 Header($ExpStr);
?>

```

...which also does not solve the "problem." Hmm.