You can access the referring url with: $_SERVER['HTTP_REFERER']
So you might be able to do something like:
<?php
@session_start();
if ($_SERVER['HTTP_REFERER'] == "https://XXXXX.com/resources/private/welcome.jsf") {
$_SESSION['referrergood'] = "yes"
}
if (!isset($_SESSION['referrergood'])) {
header("location: /badreferrer.php?ref=".$_SERVER['HTTP_REFERER']);
}
?>