While I've made every attempt to anticipate any questions you may have and answer them in this book, there is no way that any book could cover everything there is to know about PHP and MySQL. If you have a question about anything in this book that needs answering, the best place to go for a quick answer is http://www.sitepointforums.com/. Not only will you find a vibrant and knowledgeable PHP community there, but you'll occasionally even find me, the author, there in my spare hours.