Add to cart typefunctionality: How to make a processing.php for the plugin?

Ahoy,

I am looking to have an option where a vistor can save post(s) into a list and then eventually click a “view list” option to finally see the list of titles of the posts (these are items to then print out as a handy list).

In a way is it like a shopping cart, but doesn’t need any of the e-commerce requirements.

I am trying to create a plugin as I have not found that allows for this. (If you know of one please share the love)

I understand the principle involved with this, using sessions.

However, I am having a problem getting my head around the processing of the information within the wordpress plugin code. So if a person wants to click the “add to list” button, I basically want to grab “the_ID” and POST or GET it to a file, to then push it into an array ($_SESSION[‘list’]).

How do I create a “processing page”, within the plugin for this information to be processed?.