MyBB Community Forums

If I want to learn how to use php to help develop plugins and get involved here, how do I go about doing it?

I've got one book that I bought a few months ago at a sale:
Book Link

It'll take me through making basic web pages using php but doesn't get heavily into querying databases and what not.

Does anyone have any resources they'd like to share, whether online or not, that I might be able to tap into so that I can advance more and give back to the mybb community?

W3schools
Personally I find that W3 schools has good tutorials, and good reference section for each of the languages they teach you.
* PHP
* PHP/MySQL intro
* SQL

PHP Freaks has some tutorials and articles you may be interested in.

I back Dennis, I use w3schols all the time, whatever I have trouble in.

I started with http://www.hudzilla.org/phpbook/index.php a while ago and never made it past chapter 4 because I was too busy and all that sort of stuff. Nevertheless, it might be worth looking into for you.

I learned everything from experience.
When I wanted something done and I didn't know how, I just looked at how others did it. I also used php.net a lot for info on functions.

I just don't like learning from books.