With so much online documentation and support, you probably won't need more than one good PHP book. I also have Wrox's Professional PHP Programming and found it to be an excellent introduction to the language. Now that I have sort of gotten going, though, I don't really use it at all any more - when I need to find a function, I just search the manual at php.net, and when I am looking for examples of how to accomplish something, I always find that there are people willing to help, and material already available, on phpbuilder.com and many other sites.
-Keegan
P.S. Sorry for not actually answering your question!