src/Charge/Wx/WxAppCharge.php
protected function retData(array $ret)
    {
        $back = new BackAppChargeData($this->config, $ret);

        $back->setSign();
        $backData = $back->getData();

        return $backData;
    }
protected function retData(array $ret)
    {
        $back = new BackAppChargeData($this->config, $ret);

        $back->setSign();
        $backData = $back->getData();

        return $backData;
    }
处理APP支付的返回值。直接返回与微信文档对应的字段
@param array $ret

@return array $data

```php
$data = [
'appid' => '',   // 应用ID
'partnerid' => '',   // 商户号
'prepayid'  => '',   // 预支付交易会话ID
'package'   => '',  // 扩展字段  固定值：Sign=WXPay
'noncestr'  => '',   // 随机字符串
'timestamp' => '',   // 时间戳
'sign'  => '',  // 签名
];
```
@author helei