public function overwrite(&$old, $new) {
		if (!empty($old)) {
			foreach ($old as $key => $value) {
				if (!isset($new[$key])) {
					unset($old[$key]);
				}
			}
		}
		foreach ($new as $key => $value) {
			$old[$key] = $value;
		}
		return true;
	}