Include/Import config

What about include config considered a dependency which may have values referenced and thus should be processed first. The result will be a combination of settings perhaps in the form:

$result = $config + $config_include_last + $config_include_n_desc + $config_include; 

Allowing each to overwrite settings from the previous.

Now we just have to decide what an import/include looks like.
Perhaps also a header comment in order to use the same key

; import defailt.ini

or we could use an array

import = [default.ini, production.ini, app.ini]

I would rather prefer a list underneath each other though

import = $import:path/to/default.ini
matters = $import:path/to/matters.ini
not = $import:path/to/not.ini

Hmmm little weird... thoughts?

No files, tests, or entry points are named. Start by reviewing the existing configuration syntax and parser behavior, then resolve the import form, dependency ordering, and overwrite precedence proposed in the issue. Done means an agreed syntax and processing behavior are documented and covered by tests.