This is probably a good way to illustrate how programming books ought not to be written. I have high respects for the authors - especially Rasmus, all of us should be indebted to PHP founder. But, the book runs just like program documentation. Nothing wrong with it for super-geeks who learn everything from the man pages, but for the rest of us mortals there should be some mind-exercises, a few good problems, a theme to apply what we learn and what not. The book nicely goes from the basics to the more advanced concepts, but "provide it as a feature documentation" view doesn't help with the flow. The PERL camel book comes to my mind, probably writing a good teaching book requires more than just the expertise.