fluxbb/fluxbb — comment on commit da19766222c44e19b7ba1e66ec148b5655f58dae
File:  line 0
By reines:

It's perfectly valid for an interface to be empty - it's only used to indicate that a filter can also serialize (though technically the serialize interface should extend the filter interface, and then any serializers implement it only.

When you say it's in the wrong file, do you mean in terms of auto loading, or?

If you ask me the Filter.php is in the wrong place, the Cache dir was meant to be a directory only for cache implementations, which is why the filter.php and filter folder were outside it.