Try writing a blog... It's harder than it looks, but is straightforward enough to understand how to get started, at least.
So far, the best resources that I've found for each language, PHP and MySQL's version of SQL, are the sites they come from themselves...
PHP: Hypertext Preprocessor and
MySQL AB :: Developer Zone respectively.
W3Schools Online Web Tutorials also has tutorials for learning PHP and SQL, but I can't vouch for their quality... They do, however, have excellent (X)HTML and CSS tutorials, so I can't see why their other tutorials wouldn't be at the same level.
As for how long it takes... That's entirely up to you. Anywhere from a month to a lifetime.