I'm not sure about the usefulness of that feature.
If people want to signify different exit conditions, they will already have that implemented by themselves.
Because there is no standard on how to use PHP extension codes, if we use that as an exit status, we risk masking a new, uncaught exception as a specific exit code, which would be potentially disastrous.
Since `1` is a [general catch-all](http://tldp.org/LDP/abs/html/exitcodes.html), it's safe to use it.