Several interconnected forms - problem- please advice

I am setting upp several interconnected forms. Submitted information of the first form must be used in later on forms. Every time, submit by post is done, variables from that page are lost. I want to have each form in different file (.php) and need defined variables in earlier forms to be defined there. How would I go about this? It does not help to use action="<?php echo $PHP_SELF ?>" in the form field, because I still lose defined variables. Should I use classes? (I don't think they help) Please advice With thanks in advance. Helgi Jónsson helgijon@hi.is