code: public function find($partner_trade_no = '')
      {
          $this->unsetTradeTypeAndNotifyUrl();
          $this->config['partner_trade_no'] = $partner_trade_no;
          unset($this->config['appid'], $this->config['sign_type']);
          return $this->getResult($this->gateway_query, true);
      }
docs: 查询订单状态
  @param string $partner_trade_no 商户订单号
  @return array
  @throws GatewayException