Hi,
well, you can create a regular file on the server
HD, but you can also create data "on the fly"
(using a URL pointing to a PHP script, which
create, not an HTML output like usual, but an
other type of file (ASCII text for instance))
If you want to do that, you need the header()
function.
Look for examples there :
http://www.zend.com/manual/function.header.php
(at the bottom of the page)
regards,
Hervé.