Professional PHP5 by Ed Lecky-Thompson (Author), Heow Eide-Goodman (Author), Steven D. Nowicki (Author), Alec Cove (Author) is a decent PHP programming source and one I keep on my bookshelf.
Focused around PHP 5, this book is a gateway to object-oriented programming for PHP developers coming from PHP 4 or earlier. PHP 5 marked a major advance in PHP’s capabilities and you’ll get all the object-oriented programming features in this book. However, I should warn any programmer interested in this book that it is poorly written and dull. It’s educational, but your eyes will most-likely roll into the back of your head after diving into the first few chapters. I recommend looking over the table of contents in Professional PHP5 and only read chapters on topics you’re most unfamiliar with. There are some real quality nuggets of programming information in this book, like the chapter on Communicating with Users (very helpful).
This is an average coder source: Professional PHP 5
Not very engaging or well written, but it does have some good ideas on how to plan development and work with the end-user to build a quality PHP 5 application.