[MarkFL]

Try running the following query:

PHP Code:

$newusers = $vbulletin->db->query_read_slave("
    SELECT user.*
    FROM " . TABLE_PREFIX . "user AS user
    ORDER BY joindate DESC
    LIMIT 1
");

$newuser = $db->fetch_array($newusers); 


And then you should have the newest user's username in "$newuser['username']" and their userid in "$newuser['userid']".