i have a table that has users, the pages that they visited , session id and time they spent on each page.

```
session_id | talentnum    | page_name    | time
008873e0   | user1        | test.php     | 1311630222
008873e0   | user1        | test.php     | 1311630215
008873e0   | user1        | index.php    | 1311630222
008873e3   | user2        | test.php     | 1311630216
008873e3   | user2        | index.php    | 1311895032

```

how to find ouy how much time a user spent on each session

i think i should find how much the user spent on each page in a session then add the time?? i'm a bit confuze

edit. the time is the time() when they enter that page

any ideas? 
thanks