public static final function each(array $Source, callable $Callback, $keys = null): array {
		return array_walk($Source, function(&$value, $key, $keys) use ($Callback) {
			$value = count($keys) < 1 || in_array($key, $keys) ? $Callback($key, $value) : $value; },
				array_filter(Arr::simplify(array_slice(func_get_args(), 2)))) ? $Source : [];
	}