Online tutorials are probably the best, but if you are like me, you hate sitting at a computer for hours reading a book on PHP. (Unless you have a laptop of course).
The book I learned from and consider to be the best are the Sam's Teach Yourself books. I got Sam's Teach Yourself PHP, mySQL, and Apache in 24 hours. Of course it took longer than 24 hours but if you actually did read constantly for 24 hours and had a high level reading it would be possible.
Sincerely,
-Marcus