Variable definition

Thanks for all of the help.
In my php, I want to define a variable based on 2 other variables.
So, here is the code:

What I want is $menu+$submenu=$pagetitle

And what is the problem?

Well, I want to do something like this:


But that code does not work.

Ha ok (this has nothing to do with TBS)
The string concatenation operator for Php is dot.