Beginning PHP: Besides PHP, Javascript, Jquery and Mysql what else should I learn?

Ok,  here's my quick answer:

If you want to continue to learn for the future you should learn a language that has true parallel or concurrency support.  The onslaught mobile devices is only going to increase and soon the only way for any web server including those in the cloud to survive will be concurrency, parallel programming and distributed processing.

I would suggest moving your PHP knowledge over to Yaws web server and start learning Erlang, Chicago Boss Framework and MongoDB. But this is because I am biased by previous experience and using Yaws is so easy and Erlang concurrency is independent of the OS's and / or webservers multi-threading capabilities

Another good combo is Scala, Play! Framework and MongoDB.

But my question is how well do you really know the LAMP stack? Can you do pseudo parallel programming with PHP? Do you know about web services, NoSQL and XML with PHP? What about PHP in CLI? To paraphrase " there are miles to go before you sleep()" with PHP and learn something else. Unless you want to be a generalist and not an expert. I and others like myself find this very satisfying.