This book, of which I read a few chapters before returning to the library, has some excellent tips on the birds-eye view of software design with a ton of specific tips and examples and a focus on design patterns. And, obviously, is about PHP 5. The book focuses on object-oriented programming and design patterns, as the title implies, and does an excellent job of describing what each of those are, how they are described and how they can be applied.
I will come back to this book when it is time to get a bit more hands on with PHP 5 programming, there's a lot left to learn! I found the book when searching for books about PHP at the library.