I haven’t done much with XML databases but I have found SimpleXML to be extremely useful when working with XML data. PHP definitely has that nailed. I even use it for parsing WordProcessingML documents – Microsoft Office 2003′s answer to “XML” documents. It’s absolutely horrible – if you have a block of bold text you’d think there would be some sort of tag surround it, right? No, it’s a sibling tag to the text that marks it as bold. Or italic. Or anything else. It’s a nightmare, but at least it’s navigable once you throw SimpleXML into the mix.