How insert external pages, without resetting the session parameters?

[rosf]

I have included in define_main_page.php a link to an external module for an upload files, but the session ($ _SESSION etc.) Are reset in module called, so I can not use customer data to create folders upload differentiated according to customer number and order number.
Someone can help me, please, to solve this problem, with a correct example, to enter a new module in Zen-Cart, preserving the values of session variables?
Many thanks in advance.

[rosf]

This is the solution:
simply insert the pages mentioned before any other instruction, <? php require ( 'application_top.php');?>
I tested, and now everything works properly.