advanced php question

[ragefu]

Scenario.

User fills out form, clicks submit,
Users is take to page to review data they entered.
User clicks finalize and is taken to thank you page.

Question.

If the user clicks back after getting to thank you. How can I totaly expire the page so that clicking reload or back wont bring the origional page back up. IE/Mozilla/Etc.. give (Page Expired) error when this is done. Many sites do this for security andIT CAN BE DONE!.

Anyone know how?

[rohithmr]

Register a session variable in the first page.
eg:

<?php
session_start();
$_SESSION['In'] = true;
?>

Check for it in the second page where things are reviewed:

<?php
session_start();
if (isset($_SESSION['In']) && $_SESSION['In'] == true) {

// Re-list the data and let users review

} else {
header('Location: page1.php'); 
exit;
}
?>

Finally destroy the sesion variable in the thankyou page:

<?php
session_start();
session_unset();
session_destroy();
?>

Now if the user clicks the back button, it shudd not let them modify the previous pages without going to the first page first.