I don't see how this is a 'side effect'. It accomplishes the exact task it is designed to and doesn't do any quirky, or 'side', behavior to the script. Also, I

I don't see how this is a 'side effect'. It accomplishes the exact task it is designed to and doesn't do any quirky, or 'side', behavior to the script. Also, I wouldn't be worried about one lookup. I'm pretty sure everything in PHP is in a hash map.