xml_parse_into_struct() fails on all forms of RSS?

[lawrence]

I did a little test to learn about how xml_parse_into_ struct() works
and I find, to my surprise, that it fails to work at all with two
different versions of RSS. But it works with an Atom feed just fine.

Go look at this page:

http://www.publicdomainsoftware.org/xmlTest.txt

You can see the output here:

http://www.publicdomainsoftware.org/xmlTest.php

You'll note that the where the print_r() is, the Atom feed is turned
into an array, but both versions of RSS that I'm testing here come up
completely empty. Why is that?