private static function cmpCallback(array &$config, $name, array &$results)
    {
        if (!isset($config[$name])) {
            $config[$name] = function ($v, $k) use (&$results) {
                $results[$k] = $v;
            };
        } else {
            $currentFn = $config[$name];
            $config[$name] = function ($v, $k) use (&$results, $currentFn) {
                $currentFn($v, $k);
                $results[$k] = $v;
            };
        }
    }