Need data to persist through call to self

I have a script (a.php) that collects selection criteria from the user, and passes it and other arguments (via POST) to another script (b.php). B.php uses this passed data to lovingly craft and submit a MySQL statement. The returned data is displayed, the script displays data to the user, and asks if he/she wishes to re-sort it. If so, he/she clicks a link, which re-calls the same script. The problem: The data passed by a.php to b.php is no longer available. I can't use POST, because the user is not submitting a form to re-sort the data; he/she is clicking a link. Also, because I am not using a form, I cannot use HTML hidden variables. I can't use GET, because the SELECT statement is too long to append to the URL (I wouldn't want to put it there, anyway). What should I do? Save the original selection criteria in a flat file, or in a table? Save the originally selected data in a temporary table? Seems in-elegant, and wouldn't I need to identify this file or table with a session ID?