I've dabbled with PHP for a few years now and I'm capable of most of the basic things, building login forms etc but from my time on here I've noticed there's so much more I need to learn, like best practices, security issues etc and so I want to learn everything from the very basics.

In the past I've used forums and browsed the web for snippets of code only I think this has led to my bad practices, can anybody recommend books or Valid, recommended learning sources?

Thanks in advance!