About three years ago I bought PHP and MySQL Web Development ->
Amazon.com: PHP and MySQL Web Development: Books: Luke Welling,Laura Thomson and I learnt the basics (and more) in about 1 month and after about 6 months wrote my own shopping cart software which I sell to many of my clients.
I started out on the online PHP and MySQL tutorials but i found having a book to reference complete with its own tutorials sped up my learning.
It helps if you have (x)html down pat first though.