I know PHP uses COW, so theoretically, reading from a variable should have no impact on memory usage whatsoever. This has not proven to be the case, I've calle

I know PHP uses COW, so theoretically, reading from a variable should have no impact on memory usage whatsoever. This has not proven to be the case, I've called get_peak_memory_usage() and played with passing the params explicitly by reference or not. I assume it has something to do with the fact that strings/arrays are not passed by reference, and explicitly declaring the reference is cheaper sometimes and more expensive sometimes depending on refcount(maybe?)