If it wouldn't break B/C to the methods already in use (and assuming that devs copied the helper in com_content as an example), I'd say move `$urlSegments` in the declaration and not make it an optional param.  But, since it has to be where it is, simply defaulting to an empty array and documenting the array's required contents in the docblock should suffice, then checking the array and throwing a `BadMethodCallException` if those items aren't there.