前端：

Page({
    getPhoneNumber(e){
        //console.log(e.detail.code); //最新官方文档里是这个参数,很重要;
        wx.request({
            url: 'https://demo.xxxxx.com/frontapi/getphonenumber.php',
            data:{"code":e.detail.code},
            success:(res)=>{
                console.log(res.data.phoneNumber);
            }
        })
    } 
})

后端：

/*获取access_token,不能用于获取用户信息的token*/
    function getAccessToken()
    {
        $appid = '填写自己的appID';
        $secret = '填写自己的秘钥';
        
        $url = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=".$appid."&secret=".$secret."";
        
        $ch = curl_init();
        curl_setopt($ch,CURLOPT_URL,$url);
        curl_setopt($ch,CURLOPT_HEADER,0);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1 );
        curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 10);
        $res = curl_exec($ch);  
        curl_close($ch);  
        return $res;
        exit();
    }
    //图片合法性验证
    function http_request($url, $data = null)
    {
        $curl = curl_init();
        curl_setopt($curl, CURLOPT_URL, $url);
        curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, FALSE);
        curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, FALSE);

        if (!empty($data)) {
            curl_setopt($curl, CURLOPT_POST, TRUE);
            curl_setopt($curl, CURLOPT_POSTFIELDS,$data);
            curl_setopt($curl, CURLOPT_HTTPHEADER, array(
                'Content-Type: application/json'
            ));
        }
        curl_setopt($curl, CURLOPT_RETURNTRANSFER, TRUE);
        $output = curl_exec($curl);
        curl_close($curl);
        
        return $output;
        exit();
        
    }
    //  获取手机号
    function getPhoneNumber(){
        $tmp = getAccessToken();
        $tmptoken = json_decode($tmp);
        $token = $tmptoken->access_token;
        $data['code'] = $_GET['code'];

        $url = "https://api.weixin.qq.com/wxa/business/getuserphonenumber?access_token=$token";
        $info = http_request($url,json_encode($data),'json');
        // 一定要注意转json，否则汇报47001错误
        $tmpinfo = json_decode($info);
        
        $code = $tmpinfo->errcode;
        $phone_info = $tmpinfo->phone_info;
        $phoneNumber = $phone_info->phoneNumber;
        if($code == '0'){
            echo json_encode(['code'=>1,'msg'=>'请求成功','phoneNumber'=>$phoneNumber]);
            die();
        }else{
            echo json_encode(['code'=>2,'msg'=>'请求失败']);
            die();
        }
        
    }

getPhoneNumber();