I thought I was going to be able to use...
PHP:
<xen:if is="!{xen:helper ismemberof, $visitor, 2} AND {xen:helper ismemberof, $thread.user_id, 11}">
...to verify that the person watching the widget avatar is 1) not a member. In the last condition i want to verify wether the avatar showing up in the widget belongs to a member who has a premium account. If the account is premium the avatar won't show up and vice versa. For this to work I need the userID of the member who has created the thread/post. I thought I could $thread.user_id. But ismemberof function gives me the following error when I use it: