protected function myAddUser()
{
    $Root = realpath($_SERVER["DOCUMENT_ROOT"]);
    include_once $Root.'/forum_data/include/GLOBALS.php';
    include_once $Root.'/forum_data/scripts/forum_login.php';
    __fud_login_common(1); // The main point!!
    include_once $Root.'/forum_data/scripts/fudapi.inc.php';

    //use function within fudapi
    fud_add_user($arg, &err);
    .....
}