You would need to store the user group in a session variable,
then add all of the menus to the page and put an if statement around the menu.php include line to choose which menu should be used based on the user level session variable. for example, if the user level session variable is named "userLevel" the code to show the menu for User Level 1 would be:
<?php
if(!session_id()) session_start();
if($_SESSION['useLevel'] == 1){
require_once("CSSMenuWriter/cssmw/menu.php");
}
?>