I have a old website that generate its own RSS everytime a new post is created. Everything worked when I was on a server with PHP 4 but now that the host change to PHP 5, I alwa
PHP5 now comes with the SimpleXML
extension, it's a pretty quick way to build valid XML if your needs aren't complicated.
However, the problem you're suggesting doesn't seem to an issue of implementation more a problem of syntax. Perhaps you could update your question with a code example, or, a copy of the XML that is produced.