1.客戶端代碼

 // 獲取 code
  getLogin: function () {
    var that = this;
    wx.login({
      success: function (res) {
        that.getOpenId(res.code);
        console.log(res);
      }
    });
  },
  //獲取openid
  getOpenId: function (code) {
    var that = this;
    wx.request({
      url: that.url.openId,
      method: 'POST',
      header: {
        'content-type': 'application/x-www-form-urlencoded'
      },
      data: { 'code': code },
      success: function (res) {
        var openId = res.data.openid;
        console.log(res.data.openid);
        // that.xiadan(openId);
      }
    })
  },

2.后臺(tái) php端 代碼：

//    獲取openId
    function getOpenId($code)
    {
        $url = 'https://api.weixin.qq.com/sns/jscode2session?appid='
               . $this->appid . '&secret=' 
              . $this->secret . '&js_code=' 
             . $code . '&grant_type=authorization_code';
        return $this->getHTTPS($url);
    }

    //獲取https頁面信息
    function getHTTPS($url)
    {
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
        curl_setopt($ch, CURLOPT_HEADER, false);
        curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_REFERER, $url);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
        $result = curl_exec($ch);
        curl_close($ch);
        return $result;
    }

//  封裝到公共的方法之后  在其它php中調(diào)用，并返回
  public function openId()
    {
        $code = $this->request->post('code');
        echo $this->getOpenId($code);
    }