$vbulletin->userinfo[username] does not work in Subdomains

[daddel80]

I want to read the vb username for login at a new page. But it does not work. I added a test page in the menue of vb (see below).

The forum is running at http://forum.domain.com
The testpage is running http://wiki.domain.com

It is only working in older vb versions and in the same subdomain. I'm using now version 4.15 but something changed in the version that this is not running anymore on different Subdomains.

Are there any ideas how to solve that?

The output of this page is always 'Unregistered'.

PHP Code:

<?php
$current_dir = getcwd();
chdir( '/var/www/vhosts/domain.com/subdomains/forum/httpdocs' );
global $vbulletin;
require_once('./global.php');
$username = $vbulletin->userinfo[username];
echo($username);
chdir( $current_dir );

Cookie Path is /
Cookie domain is .domain.com

Thanks for any help!