Flickr has just released the serialized PHP format for API responses. This means that I can finally eliminate the troublesome XML parsers. It will very likely break any apps if you try to upgrade without doing any modifications which is why I'm moving up to version number 2.0.
The good news is that it should run a lot faster and better. It'll mean that there shouldn't be any differences between running this on PHP4 and PHP5 and international characters will all be supported correctly. I'll post an update when I manage to release it.