Defining the root directory

[Kungfu]

you could create a variable with the absolute path.

Also when including files you can use DIR if global is called or CWD. DIR should be your forum path.

You could put something in your initialize script like
$rootDIR = "website.com/public_html/root";

Then when you need it you can call it like
global $rootDIR and use that path. This way you would only edit one location to set the root.