public function toBalance(array $params)
    {
        $base = [
            'mch_id' => null,
            'mchid' => $this->app['config']->mch_id,
            'mch_appid' => $this->app['config']->app_id,
        ];

        if (empty($params['spbill_create_ip'])) {
            $params['spbill_create_ip'] = get_server_ip();
        }

        return $this->safeRequest('mmpaymkttransfers/promotion/transfers', array_merge($base, $params));
    }