Sure, there are several different ways to do it. The most famous would be expat, which works in PHP4 and 5, but it's kinda sucky. In PHP5, you've got [man]SimpleXML[/man], which does almost everything expat does in 1/40th the lines.
Then there are classes people have written, and a few other libraries.
I highly recommend SimpleXML, it's (as the name would imply) very simple.