Strange session issue in PHP

[OccafeJef]

I'm having a strange issue with sessions in PHP. Basically, when a user submits a contact form, the processing script sets a session on completion ( \[code\]$_SESSION['action']='sent';\[/code\] ). The user is then sent back to the page they sent the form from and a message is displayed using the following code:\[code\]$action = $_SESSION['action'];if ( $action == 'sent' ){echo '<p>Thank you for contacting us, we will be in touch with you ASAP.</p>';unset($_SESSION['action']);}\[/code\]The session is unset so if they refresh the page or navigate away and come back the message won't be displaying any more.Basically the problem is that when the session is unset it seems to unset it from the very beginning of the script so that the message doesn't display. The \[code\]if\[/code\] statement is obviously running as the session is being unset, but the message isn't displaying.I've used this exact same script many times before and it works absolutely perfectly on other sites (on the same server, with all the same settings).Any help/advice would be appreciated!