You might also look at <http://www.friendsofed.com/books/foundation/php/index.html>. I bought the book because it was exactly what I was looking for (Flash<->mySQL).
IMHO, a very good introduction to Flash-PHP-mySQL. It's a bit too easy for real-world implementations, but I managed to get data from mySQL via PHP to/from a Flash frontend.
They also have a discussion forum PHPforFlash.
Let me hear what you think about it!
Regards,
Peter