This only shows the last pm though you could have had multiple, anyway as your onyl selecting one use query_first instead of query and then fetch array.
PHP Code:
$latest_pm = $DB_site->query("SELECT p.privatemessageid AS pm_popup_id, p.title AS pm_popup_title, u.username AS pm_popup_username FROM privatemessage p, user u WHERE readtime = '0' AND touserid = '$bbuserinfo[userid]' AND p.fromuserid = u.userid ORDER BY dateline DESC LIMIT 1");
extract($DB_site->fetch_array($latest_pm));
can be
PHP Code:
$latest_pm = $DB_site->query_first("SELECT p.privatemessageid AS pm_popup_id, p.title AS pm_popup_title, u.username AS pm_popup_username FROM privatemessage p, user u WHERE readtime = '0' AND touserid = '$bbuserinfo[userid]' AND p.fromuserid = u.userid ORDER BY dateline DESC LIMIT 1");
extract($latest_pm);