PHP: Merge full array with empty array or check isset() first?

[BenK]

I have a few functions that should return an array, to have it merged with another array.However, sometimes there's nothing to return.What's the best scenario here?[*]Return an empty array and merge that with the full one OR[*]Return null, store the return in a variable, check that variable and THEN merge it if needed.I'm asking this because sometimes the shortest route isn't the fastest, and I don't really know what array_merge() does under the hood.