I'm aware of the benchmarks for isset() vs empty(), but I have code I need to execute only when the argument is null. This is in a function that executes many times so I'd like to optimize it.
I know that isset() is faster than empty(), but what about !isset() vs. === null? I know that the variable will exist, so I only need to test it against null.
I'm thinking of the possible penalty for the ! operator.