This needs to be plugged into a part of the site that was being used to remail a bit of info based on the lookup of an input email address in a database.

Unfortunately these pages are not making use of session data at all (yet).

Can you provide a bit of setup code I might use to set up the session such that the example code can be used?

Currently everything lives in one re-entrant php file with a form. User types email address into form and submits which reloads same file but validates the email. If email validation fails, a warning is displayed and the form appears again. If it validates, alternate content is shown instead. This is where I'd like to display the download link. I'm fine with the download link being another php file, such as "download.php" containing the code above.