This framework written in object oriented PHP4 can create RSS 2.0 feeds. Because the transformation from objects to RSS feed happens via XSLT, you can just as well transform the objects into whatever you want, if you have your own transformation file.
MagpieRSS is a simple, functional PHP inteface for parsing RSS 1.0 (and earlier versions).
Built on PHP's XML (expat) parser, and with an integrated cache for storing the parsed RSS objects, Magpie is designed by simple, and 'PHP-like' to use.