The binding of this book really is thin and tight enough to easily swat a fly--for those of you who have already bought this book, give it a try!
But really, the content of this book is hardly what one would call a reference; it's no more than a categorized list of functions with extremely short descriptions of each one. If you've ever seen or read O'Reilly's Java in a nutshell book, then you know what a reference should be like; this is not like it. I probably looked at this book a couple times only, realizing both times it could not help me.
You really can't use this book to learn PHP, and it's reference is not descriptive enough, so it's a lose-lose situation. At first I was disappointed when I ordered it online thinking I wasting away... perfectly good [money], especially since I can find all and more I need of reference at PHP.net, but then I realized this book is perfect for your bookshelf when you need a really thin book to fit in between other books to preven them from wobbling or swaying, giving a perfect snug fit. Don't buy it if you don't need it. But buy it if you don't care about wasting [money].