As other reviewers of this book have pointed out, the words "Programmer to Programmer" are easily spotted on the cover, and quite frankly, they mean it.
Professional PHP Programming is just what it sounds like: it deals with the more professional aspects of PHP. If you're totally new to web programming then you'd be better off taking in a few simple online tutorials before diving into a book like this. A knowledge of HTML is a must, and a small grasp of basic Perl (or PHP, of course) syntax and variables are both highly recommended if you want to get anything worthwhile out of this book.
Throughout the book, you're run through all you'll ever need to know about if/else statements, while (and for) loops, functions, includes, connecting to an SQL database, setting and reading cookies, sending email with PHP's built-in mail function, dynamic image generation, and the guts of "Phorum", an open-source bulletin board system written in (you guessed it!) PHP.
Take note that 5 programmers wrote this book together, and judging by some of the pictures on the cover, about 3 of them look possibly foreign. I wouldn't usually bring this up, but some of the writing is akwardly or inefficiently worded. Seems to me that some of the authors may use English as a secondary language. This can contribute to confusion, but is not a major detractor from the book as a whole.
Be forewarned: this book is huge. It costs around $40, but the price is basically justified by it's incredibly extensive coverage of the language. The book is over 900 total pages and not only covers PHP, but an introduction to what PHP is, how it works, how to install PHP and MySQL onto your computer, as well as some information on XML...which was a nice addition, but has left me a bit baffled as to how it's related to the rest of the book.
Overall if you have a decent grasp on the basics of Perl or PHP (or ASP), then this book should be perfect for you. By decent grasp, I'm referring to anyone who's read a bit on the subject, or become fairly handy at installing, editing and customizing some of the scripts out there. This book makes for decent reading and is also highly useful as a reference, which highly boosts its long-term value. If you don't have the experience necessary to comprehend this book, then I highly recommend toying around with PHP until you reach that level; you'll likely be a better programmer after having consulted this fine book.