I have developed an RSS Feed in php. (can be found at http://www.mofikiworldwide.com by clicking the rss icon in the top right)
My reason for using php to develop the feed was so that I wouldn't have to manually update a feed in an xml file everytime I needed to add something to it. It just reads a database and everytime I sbmit a new blog it auto populates the feed.
You can use IE8 I know to subscribe to the feed but most feedburner style sites can't see my feed or wont load it due to the fact that its not actually a xml file.