Sounds like you have it a bit confused - they're completely different things, in my mind. Sorry can't be specific about XML feed. But ppc is pay per click on Google Adwords, ie the right hand side of the page when you do a search. The sponsored links from the advertising fraternity.
if you want to run your own small pay per click search engine , you go to big ppc company like Miva or Kanoodle and they will provide you with xml feed where you can use it to fetch search results on your site