prevent user from accessing page

[barrowvian]

I've recently decided to use paypal standard on my site and to implement the return function so that the user goes back to my site. When the user is redirected I use php to perform some checks (like the code provided on paypal) and then move on with a bit of post paypal processing (taking some extra details and images from the user, which is then emailed to me). However, I have a small problem.....once the user submits the required details on my site they can simply press the back button and then start again, effectively allowing them to submit multiple entries when I only want to allow them to do it once. Is there anyway to prevent them from doing this? I dont want to create a login system though as its not needed.

[jamesxg1]

Maybe use sessions.

 

EG.

if(isset($_SESSION['count']))
{
header('Location: disallowed.php');
}

if(isset($_POST['submit']))
{
$_SESSION['count'] = 1;
}

 

James.