Having spent a lot on technical books over time, I can say that a few have proved invaluable, but many were just a waste of money. The invaluable books fall in the algorithms, design patterns and reference categories; few of my programming language starter books have ever been read very far. There's even a PHP book you would be welcome to, if not for the fact it would cost more to ship than the book itself did.
The type I've found to be absolutely the worst are the structured workshops and "learn something in x days". This may be a learning style issue, but I don't work like that. I don't want to read a chapter a day, diligently trying out their code examples. Instead, I want a concise yet comprehensive overview of what the language or product offers, with the shortest possible examples of how one would use each feature, and an insightful discussion of how it fits in the greater picture. I will get the minor details when I need to use it -- that's where the reference materials come in. I have found that very few programming related starter books are designed like that.
Why am I bothering to tell you all this? There are some good, basic tutorials online that you can use to get started (such as PHP and SQL tutorials
here, as well as a lot of reference material you can use to fill in the details later. You may not need a book.
If you go with the book route, I would recommend that you also pick out one on SQL in general. It doesn't need to deal with MySQL specifically; in fact, it is better that it doesn't, because most of the MySQL specific knowledge would concern administration -- which you won't be dealing with if you use third party hosting.
SQL is a very powerful language on its own and it is not likely to be well covered in any book that primarily deals with PHP. I can't count the number of times I've seen people do horrible (and complex!) things on the database client app side, which could have been trivially done on the database side, using a more intelligent SQL query. You don't want to be one of those guys.
