Problem with filename parameters

[mikawhat]

I have a form with action="<? $_SERVER['PHP_SELF'] ?>".

If the url is something like www.something.com/product_info.php?id=15 it will go to page product_info.php . I want it to go to product_info.php?id=15 . How's that possible? I could use something like action="<? $_SERVER['PHP_SELF'] ?>?id=$id" but this will not work as not all the pages have a product id parameter in the url.

[NogDog]

I might do something like this:

<?php
$url = (isset($_GET['id'])) ? '?id=' . (int) $_GET['id'] : '';
?>
<form action="<?php echo $_SERVER['PHP_SELF'].$url; ?>" method="post">

(I'm assumig the ID will always be an integer, thus my use of (int) as a quick way to screen out URL injections.)