I don't have the means to test this right now but I am curious. Using AJAX, can you open the same file that the AJAX call was on? My goal is to pretty much reload the page, with a new POST parameter, without refreshing and using only one file.
Yes you can.
I just ask you, why don't, instead of reloading the page, you reload/rebuild/destroy and create the elements you need based on the response to that ajax call ? depending on your desired outcome you might want to do it better like that. More work in the user side, but a nicer 'web 2.0' experience.