public static function diff(array $val1, array $val2) {
		if (!$val1 || !$val2) {
			return $val2 ?: $val1;
		}
		$out = array();

		foreach ($val1 as $key => $val) {
			$exists = isset($val2[$key]);

			if (($exists && $val2[$key] != $val) || !$exists) {
				$out[$key] = $val;
			}
			unset($val2[$key]);
		}

		foreach ($val2 as $key => $val) {
			if (!isset($out[$key])) {
				$out[$key] = $val;
			}
		}
		return $out;
	}