+ MySQL basics (accessing, updating, selecting, echoing things in a database)
+ OOP (Still learning it but I understand it all)
+ md5 hashing
+ Loops and if-then-else statements
+ Program readablity
+ SQL Injection and XSS (I know the basics and how to avoid most of it)
What I can create:
+ CMS with registration/login, news posts and comments, edit/view profiles, friend system
+ Contest script that allows people to register, and picks a random member
What else is there to learn? I know that when I read php.net there's a lot of things on there I don't understand but I don't know where to turn next.
More specific then just advanced, Im not sure what consititutes advanced and what I need to learn/etc.
You won't learn anything untill you encounter a task that requires advanced knowledge..you can try and find college exams regarding SQL and rewrite them to fit MySQL.
There are variety of things to learn, table joins (and why they are handy), indexes (what they are, when to use them, types), table types (advantages, disadvantages), how databases actually work, unions, subqueries, views, triggers, stored procedures etc.
Frankly speaking I don't know much on the programming side but I know some good things about search engine optimisation. But I am planning to undergo course of PHP and Ajax that will help in enhancing my knowledge further about the websites.