[Paul M]

PHP won't read/process the bold bit properly (as it's written).

        $updatefields = $vbulletin->db->query("
            UPDATE user
            SET membergroupids='12'          
            WHERE userid=$vbulletin->userinfo[userid]
        ");

Either split the variable out as a seperate string and join it, like this ;

PHP Code:

        $updatefields = $vbulletin->db->query("
            UPDATE user
            SET membergroupids='12'          
            WHERE userid=".$vbulletin->userinfo['userid'] ); 


or use a seperate simple variable, like this ;

PHP Code:

        $userid = $vbulletin->userinfo['userid'];
.
.

        $updatefields = $vbulletin->db->query("
            UPDATE user
            SET membergroupids='12'          
            WHERE userid=$userid
        ");