Prevent user of my class to worry about the session_start()



How does pear liberies hande session variables.

Seems like for example HTML/QuickForm/controller
uses $_SESSION variables but when scaning the the file there is no session_start() code anywhere.

How can it still use the session functionality.

I would like same feature to my library so users of the library do not have to worry about placing session_start()
to the pages where my class is used.
Well I just realised it was used in the example page.
Page where the class was instantiate.
I quess it just is impossible to use the session_start in my class as user might have started a header before instantiating my class..