Hi,
Changing the include_once function to file_get_contents resulted in the php code not being processed.
This change occurred in the commit below - in Cacti version 1.2.26 (same in version 1.2.27)
a2af4f8

A simple example on the php-example.html file in the /include/content directory
Instead of parsing the php code, it shows it as a comment:

Debian 9 and 12, Apache 2.4, PHP 7.0 and 8.2

Regards,
Jacek