php如何实现微信小程序支付及退款

//微信支付类

class WeiXinPay{

  //=======【基本信息设置】=====================================

  //微信公众号身份的唯一标识

  protected $APPID = appid;//填写您的appid。微信公众平台里的

  protected $APPSECRET = secret;

  //受理商ID，身份标识

  protected $MCHID = '11111111';//商户id

  //商户支付密钥Key

  protected $KEY = '192006250b4c09247ec02edce69f6a2d';

  //回调通知接口

  protected $APPURL =   'https://smart.afei.com/receivesuc';

  //交易类型

  protected $TRADETYPE = 'JSAPI';

  //商品类型信息

  protected $BODY = 'wx/book';

  //微信支付类的构造函数

  function __construct($openid,$outTradeNo,$totalFee){

    $this->openid = $openid; //用户唯一标识

    $this->outTradeNo = $outTradeNo; //商品编号

    $this->totalFee = $totalFee; //总价

  }

  //微信支付类向外暴露的支付接口

  public function pay(){

    $result = $this->weixinapp();

    return $result;

  }

   //对微信统一下单接口返回的支付相关数据进行处理

   private function weixinapp(){

     $unifiedorder=$this->unifiedorder();

     $parameters=array(

     'appId'=>$this->APPID,//小程序ID

     'timeStamp'=>''.time().'',//时间戳

     'nonceStr'=>$this->createNoncestr(),//随机串

     'package'=>'prepay_id='.$unifiedorder['prepay_id'],//数据包

     'signType'=>'MD5'//签名方式

       );

     $parameters['paySign']=$this->getSign($parameters);

     return $parameters;

   }

  /*

   *请求微信统一下单接口

   */

  private function unifiedorder(){

    $parameters = array(

      'appid' => $this->APPID,//小程序id

      'mch_id'=> $this->MCHID,//商户id

      'spbill_create_ip'=>$_SERVER['REMOTE_ADDR'],//终端ip

      'notify_url'=>$this->APPURL, //通知地址

      'nonce_str'=> $this->createNoncestr(),//随机字符串

      'out_trade_no'=>$this->outTradeNo,//商户订单编号

      'total_fee'=>floatval($this->totalFee), //总金额

      'open_id'=>$this->openid,//用户openid

      'trade_type'=>$this->TRADETYPE,//交易类型

      'body' =>$this->BODY, //商品信息

    );

    $parameters['sign'] = $this->getSign($parameters);

    $xmlData = $this->arrayToXml($parameters);

    $xml_result = $this->postXmlCurl($xmlData,'https://api.mch.weixin.qq.com/pay/unifiedorder',60);

    $result = $this->xmlToArray($xml_result);

    return $result;

  }

  //数组转字符串方法

  protected 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;

  }

  protected function xmlToArray($xml){

    $array_data = json_decode(json_encode(simplexml_load_string($xml, 'SimpleXMLElement', LIBXML_NOCDATA)), true);

    return $array_data;

  }

  //发送xml请求方法

  private static function postXmlCurl($xml, $url, $second = 30)

  {

    $ch = curl_init();

    //设置超时

    curl_setopt($ch, CURLOPT_TIMEOUT, $second);

    curl_setopt($ch, CURLOPT_URL, $url);

    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);

    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE); //严格校验

    //设置header

    curl_setopt($ch, CURLOPT_HEADER, FALSE);

    //要求结果为字符串且输出到屏幕上

    curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);

    //post提交方式