Passing a hidden customer_id to another php file

I've written a utility program to read, filter, sort, and output information from a customized table in my ZC database. I need to be able to show ALL information to customers who have bought related products, but only show SOME information to others. This means my stand-alone php file needs to know the customer_id. I don't want to pass it as a parameter, because then my logged-in customers could just copy the URL and email it to a friend and get all the privileged information. How do I give a stand-alone php file access to $_SESSION['customer_id']?

I'm using ZenCart 1.3.8a with a several add-on module and numerous amateurish custom mods.

The utility program I'm running is here

Any reason not to make it a regular /page file so that you have everything available to you?

No real reason. I hate to add any overhead I don't need, but computers are fast these days.

I guess I'd better go look up how to add it as a /page.

Well, I created a /page version of my "resource list," but I didn't like what I got. I'm trying to generate a printable table. I don't need or want the store header at the top. I really just want my nice simple php file that I already have working to be able to read session variables.

This isn't really so hard, is it?

If you want to piggy-back off the Zen Cart session data, you'll have to start the session. The easiest way to do that is to run application_top.
But, since you want to show data based on the logged-in customer details, making your script be part of a page that you've integrated into the store software would be safer and probably much more intuitive to the customer.

True... and I've been pondering the choice all afternoon. I hit a brick wall when I tried to put some javascript into the module page for my new /page. It didn't go smoothly.

As I read the directions, all I have to do is copy the proper *.js files into the /modules/page/MyPage directory. I did that and haven't seen any evidence that it worked. Are there any threads that cover this in more detail?

Perhaps you missed ensuring that the filename has a "jscript_" prefix?
http://www.zen-cart.com/wiki/index.php/Customisation_-_Templates_-_Javascript

Truly you have a dizzying intellect.

It's looking fabulous! A valuable trick to learn for all future mods. I prostrate myself before your greatness. Someday, when I can take the pebble from your hand, I will be as smart (and helpful to strangers).