^ Exactly, htaccess would do it more efficiently

Anyway, add this php code in the document and it will work (code is untested but should work)
PHP Code: 
<?php
if (isset($_GET['something'])) {
$baseurl 'http://' $_SERVER['HTTP_HOST'];
echo 
'<script language="javascript" type="text/javascript">window.location.href="' $baseurl '";</script>';
}
?>