Currently, I use a PHP script to list the contents of a directory that does not have an index file, but I don't want to have to copy it to every directory without an index.
Can Apache do it automatically?
What you're looking for, is
Make sure you have it enabled in the Apache configuration:
Note: you may have to change the path directory to the module, or even change the module name. On SOME Apache servers I've seen, it may be just:
In response to the comments: (edit)