I am mostly self taught, but having decided to get my programming certificates online from University of Illinois was the best money I ever spent to learn. You can find them here: PHP/MYSQL Course. I had more than 2 years of practice with php/mySQL prior to the course. I had used many php scripts and built several Joomla extensions. But, I had too many holes in my knowledge. After completing the course, reading and using other codes was far superior. For me, without the classes, I know I would have been far behind what I am today.
After a total of 5 years playing around with php/mySQL(including school), I now own more than 6 php books for which 5 are my main references; PHP/mySQL, PHP Programming, mysql cookbook, PHP Cookbook and PHP Object Oriented Solutions. However, php.net is my main reference.
Nowadays, with more than 5 years later practicing / developing php/mySQL applications and working full-time for a college as a php / mysql programmer, much of the learning is embedded. Writing relational database queries, outputting desired results (without references), automatically writing secure code, creating lightweight CRUD applications, and being able to edit almost all code that is not mine is finally smooth. But, I love php / mySQL and still strive to get better.
Also, I find using my custom bookmark linking script and blog really helps to keep me keep a library of code samples for which I like or would like to pass on.
Here is an example of my [web development bookmarks and [URL="http://bohemiawebsites.com/Our-Blog.html"]web development blog](http://bohemiawebsites.com/bookmarks/).