How to extract rss feed from website?

Question

PHP

Good afternoon :).
Many sites have an RSS Autodiscovery Tag:

<link rel="alternate" type="application/rss+xml" href="http://useyourinterface.com/rss">

How can I recognize it in php and pull it out (from the HTML page) useyourinterface.com/rss? (not necessarily through regexp, but I think it just won't work any other way.)
Google didn't find anything.

Answer 1

ajax.googleapis.com/ajax/services/feed/lookup?v=1....