HTML portion

How to I change the HTML portiion of a PHP script? I want to modify
the HTML portion of phpBB, and the code in there to have StatCounter
record hits to that part of my web site. I already have the main web
site logged with StatCounter, but I would like to be able to modify
the HTML portion of PHP scripts for WikiMedia and phpBB, so
I can have those logged by phpBB as well

I can see the HTML portion when I ask for the source in my
browser, but I cannot find the place in any of the PHP scripts
to change the HTML portion of the code