PHP implements the refund function of WeChat payment

<?php
/**
 * 关于微信退款的说明
 * 1.微信退款要求必传证书，需要到https://pay.weixin.qq.com 账户中心->账户设置->API安全->下载证书，证书路径在第119行和122行修改
 * 2.错误码参照 ：https://pay.weixin.qq.com/wiki/doc/api/jsapi.php?chapter=9_4
 */
header(&#39;Content-type:text/html; Charset=utf-8&#39;);
$mchid = &#39;xxxxx&#39;;     //微信支付商户号 PartnerID 通过微信支付商户资料审核后邮件发送
$appid = &#39;xxxxx&#39;; //微信支付申请对应的公众号的APPID
$apiKey = &#39;xxxxx&#39;;  //https://pay.weixin.qq.com 帐户设置-安全设置-API安全-API密钥-设置API密钥
$orderNo = &#39;&#39;;           //商户订单号（商户订单号与微信订单号二选一，至少填一个）
$wxOrderNo = &#39;&#39;;           //微信订单号（商户订单号与微信订单号二选一，至少填一个）
$totalFee = 0.01;          //订单金额，单位:元
$refundFee = 0.01;         //退款金额，单位:元
$refundNo = &#39;refund_&#39;.uniqid();    //退款订单号(可随机生成)
$wxPay = new WxpayService($mchid,$appid,$apiKey);
$result = $wxPay->doRefund($totalFee, $refundFee, $refundNo, $wxOrderNo,$orderNo);
if($result===true){
  echo &#39;refund success&#39;;exit();
}
echo &#39;refund fail&#39;;
class WxpayService
{
  protected $mchid;
  protected $appid;
  protected $apiKey;
  public $data = null;
  public function __construct($mchid, $appid, $key)
  {
    $this->mchid = $mchid; //https://pay.weixin.qq.com 产品中心-开发配置-商户号
    $this->appid = $appid; //微信支付申请对应的公众号的APPID
    $this->apiKey = $key;  //https://pay.weixin.qq.com 帐户设置-安全设置-API安全-API密钥-设置API密钥
  }
  /**
   * 退款
   * @param float $totalFee 订单金额 单位元
   * @param float $refundFee 退款金额 单位元
   * @param string $refundNo 退款单号
   * @param string $wxOrderNo 微信订单号
   * @param string $orderNo 商户订单号
   * @return string
   */
  public function doRefund($totalFee, $refundFee, $refundNo, $wxOrderNo=&#39;&#39;,$orderNo=&#39;&#39;)
  {
    $config = array(
      &#39;mch_id&#39; => $this->mchid,
      &#39;appid&#39; => $this->appid,
      &#39;key&#39; => $this->apiKey,
    );
    $unified = array(
      &#39;appid&#39; => $config[&#39;appid&#39;],
      &#39;mch_id&#39; => $config[&#39;mch_id&#39;],
      &#39;nonce_str&#39; => self::createNonceStr(),
      &#39;total_fee&#39; => intval($totalFee * 100),    //订单金额  单位 转为分
      &#39;refund_fee&#39; => intval($refundFee * 100),    //退款金额 单位 转为分
      &#39;sign_type&#39; => &#39;MD5&#39;,      //签名类型 支持HMAC-SHA256和MD5，默认为MD5
      &#39;transaction_id&#39;=>$wxOrderNo,        //微信订单号
      &#39;out_trade_no&#39;=>$orderNo,    //商户订单号
      &#39;out_refund_no&#39;=>$refundNo,    //商户退款单号
      &#39;refund_desc&#39;=>&#39;商品已售完&#39;,   //退款原因（选填）
    );
    $unified[&#39;sign&#39;] = self::getSign($unified, $config[&#39;key&#39;]);
    $responseXml = $this->curlPost(&#39;https://api.mch.weixin.qq.com/secapi/pay/refund&#39;, self::arrayToXml($unified));
    $unifiedOrder = simplexml_load_string($responseXml, &#39;SimpleXMLElement&#39;, LIBXML_NOCDATA);
    if ($unifiedOrder === false) {
      die(&#39;parse xml error&#39;);
    }
    if ($unifiedOrder->return_code != &#39;SUCCESS&#39;) {
      die($unifiedOrder->return_msg);
    }
    if ($unifiedOrder->result_code != &#39;SUCCESS&#39;) {
      die($unifiedOrder->err_code);
    }
    return true;
  }
  public static function curlGet($url = &#39;&#39;, $options = array())
  {
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_TIMEOUT, 30);
    if (!empty($options)) {
      curl_setopt_array($ch, $options);
    }
    //https请求 不验证证书和host
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
    $data = curl_exec($ch);
    curl_close($ch);
    return $data;
  }
  public function curlPost($url = &#39;&#39;, $postData = &#39;&#39;, $options = array())
  {
    if (is_array($postData)) {
      $postData = http_build_query($postData);
    }
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $postData);
    curl_setopt($ch, CURLOPT_TIMEOUT, 30); //设置cURL允许执行的最长秒数
    if (!empty($options)) {
      curl_setopt_array($ch, $options);
    }
    //https请求 不验证证书和host
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
    //第一种方法，cert 与 key 分别属于两个.pem文件
    //默认格式为PEM，可以注释
    curl_setopt($ch,CURLOPT_SSLCERTTYPE,&#39;PEM&#39;);
    curl_setopt($ch,CURLOPT_SSLCERT,getcwd().&#39;/cert/apiclient_cert.pem&#39;);
    //默认格式为PEM，可以注释
    curl_setopt($ch,CURLOPT_SSLKEYTYPE,&#39;PEM&#39;);
    curl_setopt($ch,CURLOPT_SSLKEY,getcwd().&#39;/cert/apiclient_key.pem&#39;);
    //第二种方式，两个文件合成一个.pem文件
//    curl_setopt($ch,CURLOPT_SSLCERT,getcwd().&#39;/all.pem&#39;);
    $data = curl_exec($ch);
    curl_close($ch);
    return $data;
  }
  public static function createNonceStr($length = 16)
  {
    $chars = &#39;abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789&#39;;
    $str = &#39;&#39;;
    for ($i = 0; $i < $length; $i++) {
      $str .= substr($chars, mt_rand(0, strlen($chars) - 1), 1);
    }
    return $str;
  }
  public static function arrayToXml($arr)
  {
    $xml = "<xml>";
    foreach ($arr as $key => $val) {
      if (is_numeric($val)) {
        $xml .= "<" . $key . ">" . $val . "</" . $key . ">";
      } else
        $xml .= "<" . $key . "><![CDATA[" . $val . "]]></" . $key . ">";
    }
    $xml .= "</xml>";
    return $xml;
  }
  public static function getSign($params, $key)
  {
    ksort($params, SORT_STRING);
    $unSignParaString = self::formatQueryParaMap($params, false);
    $signStr = strtoupper(md5($unSignParaString . "&key=" . $key));
    return $signStr;
  }
  protected static function formatQueryParaMap($paraMap, $urlEncode = false)
  {
    $buff = "";
    ksort($paraMap);
    foreach ($paraMap as $k => $v) {
      if (null != $v && "null" != $v) {
        if ($urlEncode) {
          $v = urlencode($v);
        }
        $buff .= $k . "=" . $v . "&";
      }
    }
    $reqPar = &#39;&#39;;
    if (strlen($buff) > 0) {
      $reqPar = substr($buff, 0, strlen($buff) - 1);
    }
    return $reqPar;
  }
}
?>