[development] Temporary form data storage ... and avoiding validation

[Daniel F. Kudwien]

> > Is form_state going to persist the user data for me 
> > between form loads, or is there a better method?
...
> You can safely use the form_state array to store your 
> temporary data, but remember that the form cache has only 6 
> hours to live.

The form cache only stores data for a single form submission attempt, bound
to form_build_id.  Each time the form is built from scratch in a GET
request, a new form_build_id is generated, and the form may be cached, but
it is not supposed to re-display any previously submitted values that were
cached for a different form_build_id.

Your shopping cart use-case sounds like $_SESSION or a dedicated table keyed
by session ID and uid to me.  Also not sure why you want to reinvent the
wheel -- doesn't Ubercart or eCommerce or anything else in contrib contain a
ready Cart module already?

sun