I've been programming in PHP for about a year and am at the following stage:
Have a good 'feel' for the language
Can create CRUD applications competently
Can utilize an MVC structure to allow for future expansion of code
Using the points listed above, I've created a number of my own applications for practise - including but not limited to; a forum, social network etc.
My question may be a little vague but should hopefully be answerable.
I feel as though there isn't anything else I would need to know about PHP to allow me to create websites, though I'm sure I'm wrong.
What advanced/complex PHP topics could I look at that have a real-world use and will allow me to enhance both my skill as a programmer and applications in general?