The recipes may be used in your own projects, and you may modify them, without giving any attribution (though you can if you want). Using these recipes can saves time from "reinventing the wheel".
A companion site is given, where all recipes can be downloaded, along with example files to experiment/play with, though you'll need a web server with PHP, but you can easily run one on your desktop by installing one of the packages that make it easy (more in chapter 1).
One thing I would have liked to see is more discussion about performance issues. Some of the PHP recipes seem like they may be CPU intensive, like the spell checking recipe (PHP #8) and some of the recipes that use regular expressions in loops (PHP #3). I also found some inaccuracies/typos, but they were relatively few and minor. There were also a few instances of what I would consider "bad advice" (like suggesting you can do something that results in corrupted HTML (PHP #49). However, in the grand scheme of things these issues do not detract much from the overall value of the book.
Even if you just use a few recipes from the book, this book could pay for itself in the time saved from "reinventing the wheel" or from preventing a security "disaster" that you may not have otherwise prevented by writing your own recipe. You'll probably also discover some techniques, methods, and solutions to problems that that you might not have otherwise thought of (which is always a good thing for a web developer with jobs to do and problems to solve).
Overall this 975 page book contains A LOT of useful "recipes" (which you can modify if needed) with a great potential to learn a lot just by reading the book and studying the recipes & explanations. 5 stars overall.