The only problem with this book, apart from the usual issues with shallowness that are virtually unavoidable when covering such a wide topic, is the fact that it is increasingly out-of-date. That is not to say that anything in it is wrong; the changes to the interface of PHP are generally backwards-compatible, especially when you correctly use the preprocessor macros as described. Rather, there are new, more powerful ways to do a lot of things that would be really useful to have covered as clearly as the contents of this book are covered here.
Perhaps the author and publisher will consider an updated edition after the next major update to PHP, as there are some fairly important changes already in (namespaces) and coming up.