PHP function problem

[DreX]

http://pastebin.com/FRHQSXq5
Can anyone tell me why this wont echo:
-the first three arrays are doing nothing since I wanted to test functions out on something simpler first.

add function: 8
sub function: 2

Instead I get:

add function: 
sub function:

Also, is there a way I can track my code line by line and check the values like I can in NetBeans with Java?

[DreX]

NVM, no return command in the sub and add functions.