Sessions

[Nitestarz78]

I have an "Email a Friend" form that captures the referring url and saves it in a session.  The problem is that if someone decides not to send the form and navigates away from the page, and then decides to email another page, it saves the previous url.  How can I have it so that it clears the previous url and uses the new one?

 

if(!isset($_SESSION['referrer'])){
//get the referrer
if ($_SERVER['HTTP_REFERER']){
$referrer = $_SERVER['HTTP_REFERER'];
}
else{
$referrer = "http://www.mcse-training-classes.com";
}
//save it in a session
$_SESSION['referrer'] = $referrer; 
}