如果复制你无法用，请看看小程序公众后台，功能-微信支付 是否绑定支付商户号

接口方法

php">    public function feer(){
        include_once("WeixinPay.php");
        $appid=''; //小程序appid
        $openid= $_GET['openid'];
        $mch_id=''; //微信支付商户支付号
        $key=''; //Api密钥
        $out_trade_no = $mch_id. time();
        $total_fee = $_GET['fee'];
        if (empty($total_fee)) { //押金
            $body = "充值押金";
            $total_fee = floatval(99*100);
        } else {
            $body = "充值余额";
            $total_fee = floatval($total_fee*100);
        }
        $weixinpay = new WeixinPay($appid,$openid,$mch_id,$key,$out_trade_no,$body,$total_fee);
        $return=$weixinpay->pay();

        echo json_encode($return);
//        return json_encode($return);
    }

写个类直接放入接口同个controller类目即可 WeixinPay.php

php"><?php

/*
* 小程序微信支付
*/

class WeixinPay
{

    protected $appid;
    protected $mch_id;
    protected $key;
    protected $openid;
    protected $out_trade_no;
    protected $body;
    protected $total_fee;

    function __construct($appid, $openid, $mch_id, $key, $out_trade_no, $body, $total_fee)
    {
        $this->appid = $appid;
        $this->openid = $openid;
        $this->mch_id = $mch_id;
        $this->key = $key;
        $this->out_trade_no = $out_trade_no;
        $this->body = $body;
        $this->total_fee = $total_fee;
    }

    public function pay()
    {
//统一下单接口
        $return = $this->weixinapp();
        return $return;
    }


//统一下单接口
    private function unifiedorder()
    {
        $url = 'https://api.mch.weixin.qq.com/pay/unifiedorder';
        $parameters = array(
            'appid' => $this->appid, //小程序ID
            'mch_id' => $this->mch_id, //商户号
            'nonce_str' => $this->createNoncestr(), //随机字符串
//            'body' => 'test', //商品描述
            'body' => $this->body,
//            'out_trade_no' => '2018013106125348', //商户订单号
            'out_trade_no' => $this->out_trade_no,
//            'total_fee' => floatval(0.01 * 100), //总金额 单位 分
            'total_fee' => $this->total_fee,
            'spbill_create_ip' => $_SERVER['REMOTE_ADDR'], //终端IP
// 'spbill_create_ip' => '192.168.0.161', //终端IP
            'notify_url' => 'https://www.weixin.qq.com/wxpay/notify.php', //通知地址  确保外网能正常访问
            'openid' => $this->openid, //用户id
            'trade_type' => 'JSAPI'//交易类型
        );
//统一下单签名
        $parameters['sign'] = $this->getSign($parameters);
        $xmlData = $this->arrayToXml($parameters);
        $return = $this->xmlToArray($this->postXmlCurl($xmlData, $url, 60));
        return $return;
    }


    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($ch, CURLOPT_RETURNTRANSFER, TRUE);
//post提交方式
        curl_setopt($ch, CURLOPT_POST, TRUE);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $xml);
        curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 20);
        curl_setopt($ch, CURLOPT_TIMEOUT, 40);
        set_time_limit(0);
//运行curl
        $data = curl_exec($ch);
//返回结果
        if ($data) {
            curl_close($ch);
            return $data;
        } else {
            $error = curl_errno($ch);
            curl_close($ch);
            throw new WxPayException("curl出错，错误码:$error");
        }
    }


//数组转换成xml
    private function arrayToXml($arr)
    {
        $xml = "<xml>";
        foreach ($arr as $key => $val) {
            if (is_array($val)) {
                $xml .= "<" . $key . ">" . arrayToXml($val) . "</" . $key . ">";
            } else {
                $xml .= "<" . $key . ">" . $val . "</" . $key . ">";
            }
        }
        $xml .= "</xml>";
        return $xml;
    }


//xml转换成数组
    private function xmlToArray($xml)
    {
//禁止引用外部xml实体
        libxml_disable_entity_loader(true);
        $xmlstring = simplexml_load_string($xml, 'SimpleXMLElement', LIBXML_NOCDATA);
        $val = json_decode(json_encode($xmlstring), true);
        return $val;
    }


//微信小程序接口
    private function weixinapp()
    {
//统一下单接口
        $unifiedorder = $this->unifiedorder();
//        print_r($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
        );
//签名
        $parameters['paySign'] = $this->getSign($parameters);
        return $parameters;
    }


//作用：产生随机字符串，不长于32位
    private function createNoncestr($length = 32)
    {
        $chars = "abcdefghijklmnopqrstuvwxyz0123456789";
        $str = "";
        for ($i = 0; $i < $length; $i++) {
            $str .= substr($chars, mt_rand(0, strlen($chars) - 1), 1);
        }
        return $str;
    }

//作用：生成签名
    private function getSign($Obj)
    {
        foreach ($Obj as $k => $v) {
            $Parameters[$k] = $v;
        }
//签名步骤一：按字典序排序参数
        ksort($Parameters);
        $String = $this->formatBizQueryParaMap($Parameters, false);
//签名步骤二：在string后加入KEY
        $String = $String . "&key=" . $this->key;
//签名步骤三：MD5加密
        $String = md5($String);
//签名步骤四：所有字符转为大写
        $result_ = strtoupper($String);
        return $result_;
    }


///作用：格式化参数，签名过程需要使用
    private function formatBizQueryParaMap($paraMap, $urlencode)
    {
        $buff = "";
        ksort($paraMap);
        foreach ($paraMap as $k => $v) {
            if ($urlencode) {
                $v = urlencode($v);
            }
            $buff .= $k . "=" . $v . "&";
        }
        $reqPar = '';
        if (strlen($buff) > 0) {
            $reqPar = substr($buff, 0, strlen($buff) - 1);
        }
        return $reqPar;
    }


}

前端

    wx.request({
      url: api.url + 'feer', //请求接口的url
      method: 'GET', //请求方式
      data:{
        openid: app.globalData.openid,//获取用户openid  必须要获取到openid
        fee:100 //商品价格
      },
      header: {
        'content-type': 'application/json' // 默认值
      },
      success: function (res) {
        console.log(res.data);
        console.log('调起支付');
        wx.requestPayment({
          'timeStamp': res.data.timeStamp,
          'nonceStr': res.data.nonceStr,
          'package': res.data.package,
          'signType': 'MD5',
          'paySign': res.data.paySign,
          'success': function (res) {
            console.log('success');
            wx.showToast({
              title: '支付成功',
              icon: 'success',
              duration: 3000
            });
          },
          'fail': function (res) {
            console.log(res);
          },
          'complete': function (res) {
            console.log('complete');
          }
        });
      },
      fail: function (res) {
        console.log(res.data)
      }
    });