HI, everyone!

I was watching Bucky's tutorials a lot and i love them, now I have a question that bothers me these last days.

I'm a graphic/web designer and front end developer, but I'm studding Computer science.

I am kinda photoshop/illustrator expert and coreldraw as well.
I learned HTML,CSS,javascript coding and know I can mostly do any website frontend programming.

but since I am studding computer science I wanted to always to be a backend programmer. (because of the University)

Now I want to learn a new programming language and don't know what is better for me to learn, I like java (and can program some things) but I thing its better for me to learn PHP.

As I know i can program with java in web and windows, but PHP just web? java is I think better for the market because companies pay more for java or C# then PHP? 

What do you guys think I should do?