Database data feed

I have a database using PHP and MySQL to display Real Estate listings. I want to export listings (I think I can handle this quite easily to export to a csv file.) I want to have the data formatted in XML to be uploaded to a 3rd party site like zillow.com. I have a total of 5 different sites I want to upload files to and each one is a little different. So, if I can have something done I would guess in php that I could edit to be able to accomodate all of the different feeds, that may be the simplest. Let me know what you think.