If I could only pick one book, it would be PHP Pocket Reference 2nd Ed by Rasmus Lerdorf, ISBN 0596004028 which sits on my desk and which I use everyday. In general, the O’Reilly Pocket Reference series of books all demand a place on my desk.
The best beginner or starter book is MySQL/PHP Database Applications by Greenspan and Bulger, ISBN 0764535374. This book is an excellent overview of both PHP and MySQL. Chapter 3, Getting What You Want with Select is tremendously useful, both in explaining how to do some tricky stuff, and in explaining how MySQL differs from other SQL databases. If I could only pick two books, this would be the second.
Two other O’Reilly Pocket Reference books also on my desk and in constant use are the HTML Pocket Reference by Niederst ISBN 0596002963 which documents the HTML you need to know to build web apps, and the JavaScript Pocket Reference by Flanagan ISBN 0596004117 which documents some of the extra stuff you need to know to get simple client-side scripts and stuff to work right. Although, frankly, I do some really gory stuff with JavaScript that goes way beyond client side field validation.
The best reference book is Programming PHP by Lerdorf and Tatroe ISBN 1565926102 published, of course, by O’Reilly. Note that it doesn’t really cover any MySQL at all.
A good SQL reference book is SQL in a NutShell by Kline and Kline ISBN 1565927443 and it covers all SQL databases, highlighting the differences between MySQL and the others. Also published by O’Reilly. I tend to use Chapter 3 in MySql/PHP Database Applications as my reference of first resort, and then go to this one if I need more help.
One of the first PHP/MySQL books I bought was Web Application Development with PHP 4.0 by Ratschiller and Gerken ISBN 0735709971. This book was written by the guys at phpwizard.net and the authors of phpMyAdmin which is the development tool you must get and use. On the other hand, while you need phpMyAdmin you probably don’t need this book.
I also have PHP and MySql Web Development by Welling and Thomson ISBN 0672317842 which is not very good at all.
