ilias session handling problem
 

hi
i am using two open source in my project
ILIAS for lms
Forum for phpbb

www.xyz.com
www.xyz.com/lms
www.xyz/forum/

when i login my site
2 option show forum and lms
when i click forum user is all ready logged there
come back to main site session working good
but when i click on lms automatically user logged in lms
but when i came bake on main site session not working of my coded part but forum and lms session is still working

my coding style is
session_start();
check on database is user is valid
then
$_session['user_id]=$row->user_id;(for example)

what is problem please help me