[development] something interesting about isset and array_key_exists

Hi! As you might know, isset is preferred over array_key_exists because isset being a language construct it's a lot faster. I was under the impression that isset($array['foo']) and array_key_exists('foo', $array) is the same all the time. However, it's not. Yes, that's documented in the PHP manual but I think it's worth mentioning because we are now working with arrays a lot more: isset() does not return TRUE for array keys that correspond to a NULL value, while array_key_exists() does. Regards NK