FileReference Download File Type

Hi, i checked on the adobe as 2.0 reference docs for fileReference download method. It states:
“This method supports downloading of any file type, with either HTTP or HTTPS. You can also send data to the server with the download() call by appending parameters to the URL, for the server script to parse.”

I’m trying to get a file to download of a certain type (an XML file), at the moment i just parse a file name of testFile.xml into the download method - this works as long as the user does not change the filename being saved in the file browser.

I find the reference doc a little vague, by “appending parameters to the URL, for the server script to parse.” does it mean I would have to parse this to say a php file first?

I hope someone can point me in the right direction so I can achieve a download where the filetype is prespecified.