I've worked with PHP for almost 7 years now, and I have never actually sat down and read a book that covers design patterns specifically for PHP; however, I am familiar with them from my work experience as you can't help but pick them up if you do any sort of regular OOP programming. I must admit that I agree with many of the other reviews in saying that the examples can span from over-simplistic to extremely convoluted; however, the explanations of concepts is decent enough that someone with little knowledge of OOP could get a head start with this book.
Now, I mention someone with no knowledge of OOP can benefit; however, that does not extend to someone with no or little PHP experience. This book is honest from the beginning when it states it expects the reader to be rather proficient with PHP coming into the book. It is not going to teach you anything new about PHP unless perhaps you have never worked with OOP + PHP in which case the opening section of the book can be rather helpful (although the book "Programming PHP" would be a better recommendation to pick up the basics of OOP in an PHP environment). It almost requires a reader to already be familiar with not only PHP but OOP principles in general.
I feel the previous reviewers expected something from this book that the book does not even promise. You will not learn what OOP is or how PHP works in this book; what you will learn, however, is Design Patterns in a PHP environment. That's it. That is the value of this book, and it is also the title of the book "Learning PHP Design Patterns". It does what it claims to do, and that is introduce the reader to basic OOP Design Patterns in the context of PHP. If you expect anything else from this book you will be disappointed. There are other sources to learn about OOP and PHP, but this is a decent enough source for OOP Design Patterns in PHP.