[PHP] how can i use sessions with frames

[phptom]

Hi folks,
 
I want to use a frameset with two frames, one leftFrame and one
rightFrame. sometimes i need to change both frames at the syame time.
 
the loginpage is a single frame window.
 
 
How do i have to write my php code to prevent all these session errors. 
 
session already startet in ..... on line ...
headers already sent in ....
set_cookie already sent ....
 
Thanks 
 
Tom