[UPHPU] include() outside root

[Timothy Humphrey]

Is there a way to include() a file outside the document root from a 
file that is referenced in several files, each in a different level of 
the directory?

I reread that question and realized that it's hard to understand; so 
I'll give an example:

/root/website/backend.php
<? include(../config.php); ?>

/root/website/file_1.php
<? include(backend.php); ?>

/root/website/folder/file_2.php
<? include(../backend.php); ?>

In my experience, file_2.php gives an error finding config.php from 
backend.php on line 1.

Thank you.
Timothy