I've decided to disclose my opinion on this book after a discouraged Italian ZCE candidate contacted me through my personal e-mail asking for help, having failed 3 out of 3 mock tests he had taken. He had prepared himself with this book only ...and now you can probably imagine already where this review will end... but let's move on anyways...
The book is actually a pretty good, smooth to read, primer to PHP, even containing several useful tips here and there; unfortunately if fails to accomplish its main intended purpose, since it doesn't cover all the topics required to pass both the Zend mock and real ZCE exams. PHP basics (Chapter 1) can give you a good overview of PHP; Chapter 7 (Database Programming) and Chapter 9 (XML and Web Services) can also give you a pretty decent preparation, but unfortunately that's where the completeness of this book in terms of preparation for the exam ends.
All other topics require in fact that you deeply dig contents from other sources; in particular, the Streams and Network Programming chapter is, in my opinion, very vague and could be considered as interesting and useful only if it was contained inside of an introductory book to PHP, definitely not so for for a certification study guide; similar considerations, even if to a lesser extent, apply for the Strings and OOP chapters also.
MAIN SOURCES OF DISAPPOINTMENT:
What has actually been even more disappointing about this book for me is that the whole preparation path you'd typically expect from a study guide is completely lacking: there are no practice questions, exercises or references to external sources, where what you'll be asked is explained; it'd have been simple to say: "you need to know at least what every function dealing with strings and arrays does, so just head to the official PHP website and read such extracts from the official manual". But there's actually even more to it ...the simple code snippets included in the book do contain errors, which can sometimes cause big headaches while studying, unnecessarily complicating your preparation pathway.
It's my belief that you should NOT rely solely on this book for your Zend Certification preparation. For the aforementioned reasons, I really can't understand how other reviewers who stated that they passed the certification exam thanks to this book alone, managed to accomplish such a thing; at the same time, I also do not agree with others who stated that you need to take the official courses in order to pass; you can definitely pass the exam without taking an expensive class. What you can do is getting some mock exams, sample out a couple of them to understand what you'll be asked and then study from different sources. Chapters 7 & 9 from this book constitute pretty good material, but make sure you also read the online php documentation (you have to know about streams and network programming, about the main settings of the php.ini file, about SUPERGLOBALS, about variable scope, about the http protocol, what all strings and arrays functions do, plus their parameters and return values) and possibly some other useful good books (for exampleI've found PHP Objects, Patterns, and Practice, Second Edition by M. Zandstra to be very usefulj and interesting), especially in the parts which cover the topics (OOP, PHP 4/5 differences) listed on the Zend official website at the Exam Information page (there's actually a quite detailed list of things you're expected to know there).
And yeah... as about this book... what I can suggest you to do is to definitely get it if you have some extra bucks in your pocket, since it is actually useful for certain topics and possibly during the reviewing phase of your preparation. If I had to choose between this book and a set of mock exams though, I'd definitely pick the latter and use zend.com (Exam Information page) and [...]as my study guides. Of course, just my 2c here...