Strophe and zombie session, how to delete session direct from DB?

Hi,

I’m using openfire with strophe (library than allow me connect to openfire via web). I have problem with sessions. Sometimes openfire shows active sessions though users logged out. The connection went across http-bind. To do my application more attractive there is also PHP application which allows users to log into panel and manage profiles etc. My question is - how to delete openfire sessions directly from database? Is there any chance to do that? I’ve tried to list active user by MySQL query like:

SELECT *
FROM `ofUser`
WHERE username NOT
IN ( SELECT username
FROM ofPresence
)
AND (
ofUser.username NOT LIKE '%vis-%'
AND ofUser.username NOT LIKE '%ju-%'
)
LIMIT 0 , 30

but there are listed more users that in session summary tab in openfire admin panel. One more question is that the table ofPresense shows users online, or openfire makes any other steps to detects sessions?

Sorry for my poor english ;/