Include php file, access outside web root

I want to include a file using {{file::....php}} but I get an error.

The php file needs access outside web root:

require 'vendor/autoload.php';
use net\authorize\api\contract\v1 as AnetAPI;
use net\authorize\api\controller as AnetController;

Can this be done?

That should not be necessary. Those files should be autoloaded already.