If you want advanced stuff, you have to move away from PHP book and buy books that deal with general programming stuff. Programming is not just "programming" though. There are many different things you might want to focus on. You could read about algorithms and make your stuff run fast. You could read about things like semantics and lambda calculus to get a better idea of what exactly a programming language is. Maybe things like computability would be interesting, i.e. what is it possible to compute, and can it be done within reasonable time (has a lot to do with algorithms as well). Maybe you would find concurrency and making things run in parallel interesting. Or you might be interested in how to make well designed applications, or how to manage programming projects.
There are so many things to programming that it's difficult suggesting an "advanced" book. I might suggest Introduction to Algorithms, but if algorithms aren't really your thing, you might find The Pragmatic Programmer more interesting. Both books can be said to be related to programming, but they are very different books.
Makes a very important point. You will have trouble finding 'advanced php' books because php itself is not that advanced of a programming language. I sometimes find myself switching off from time to time when I'm programming in php because it's so damn easy when you 'know' it. The only challenge now is keeping on top of modern web technologies.
Programming in general: the rabbit hole goes very deep. Hurts my head.
Oh, I'd also second that pragmatic programmer. This is one of THE best programming books I've ever read. You can see other recomendations here:
Code Complete and Pragmatic Programmer!
For php: Php 5 Objects Patterns and Practice by that matt guy.