They say...
Thanks for your reply. Any PHP script in your hosting package can be run on the command line via the PHP exec() function, and can make connections locally to the MySQL process on the server - therefore a sitemap generator could be written to generate a sitemap from your database and/or your PHP scripts and other files, depending on how your data is organised. Unless one exists, I wouldn't recommend writing one, however, and would recommend running a sitemap generator externally.