PHP is an open source, server-side, HTML-embedded scripting language used to create dynamically generated Web pages. With an easy-to-use syntax and a large, extensible library of modules, PHP makes it fast and easy to create powerful data-driven Web sites for e-commerce, community portals, and other Web-based applications.
The PHP Developer's Cookbook is a task-based reference designed to give developers easy-to-follow solutions to common problems they might encounter. Each solution provides complete code listings along with an in-depth explanation of how and why a particular solution was used.
This book is in the unique position of being a combination of a reference manual and an instructional text. Although it is not a complete reference, it does cover previously undocumented material, and supplements the documentation for many functions. And even though it is not an instructional text, reading this book will make you a better programmer, and give you a more solid approach to problem solving.
This book should not be your only reference for PHP, but rather it should be a supplement. If you are looking for a printed reference, I highly recommend Leon Atkinson's Core PHP, published by Prentice Hall, and Rasmus Lerdorf's PHP: Pocket Reference, published by O'Reilly.
On the flip side, this book should not be your introduction to PHP. This book assumes a basic level of competence in and understanding of the PHP language. If you're looking for a good introduction to PHP, check out PHP Fast & Easy Web Development by Julie Meloni.
This book has no logical progression, so you can pick it up at any recipe and it will make as much sense as if you had started at the beginning. This is a cookbook, so when you need to know how do to something, you should just look up the appropriate recipe (either in the Table of Contents or the index) and turn to the appropriate page.