Usually the
"listener" is in the
/event/
directory and not your functions used through out your extension.
However, have a look at the
Board Rules ACP Module, Line 30. You can use the
phpbb_container
to get a service, which is declared within your
services.yml
.
Or if you're working with an admin controller yourself, which is declared in your
services.yml
, you can add the functions file through a dependency.
You can read more about that
in the 3.2.x Extension Docs.