Thanks very much for your answer. Yes, for subsequent requests the parameters are gone, redirectBack() is already a subsequent request I suppose. Does that mean I cannot use SilverStripe forms in that way? I cannot process a form and show content depending on whether a checkbox in that form has been ticked? - Unless I first write it in a database, cookie or Session (Session::set stores the data in a cookie I think?).
What I wanted to do is ask people to tick a box, and only if that box is ticked they get redirected to the same page showing different content - or other page. But that page should not be accessible by directly calling the URL. Can you give me an idea how best to achieve that?
Thanks again
Katja
P.S. For a moment I was not sure anymore if one can even do it in just PHP, so I wrote this little example. So what I mean is, how could I get the behaviour this script displays, but using SilverStripe? I'm sure it must be possible, but I couldn't figure it out so far.
<?php
if(isset($_POST["accept"])) {
echo $_POST["accept"];} else {
?>
<form method="post" action="">
<input type="checkbox" name="accept" id="accept" />
<label for="accept">I accept the Terms and Conditions</label><br />
<input type="submit" value="Submit" title="Submit" />
</form>
<?php
}
?>