<button bindtap='login'>獲取code與openID</button>
<text>code:{{code}}</text>
<text>openID:{{openid}}</text>
<text>session_key:{{session_key}}</text>

Page({
  data: {
    code:"",
    openid:"",
    session_key:""
  },
  login:function(){
    var that=this;
    wx.login({
      success:function(log){
        console.log(log.code);
        that.setData({
          code:log.code
        });
        wx.request({
          url: 'test.php',
          data:{code:log.code},
          success:function(data){
            console.log(data);
            that.setData({
              openid: data.data.openid,
              session_key: data.data.session_key
            });
          }
        })
      }
    })
  }
})
 

<?php
//宣告CODE，獲取小程式傳過來的CODE
$code = $_GET["code"];
//配置appid
$appid = "修改成你小程式的APPID";
//配置appscret
$secret = "修改成你小程式的APPSECRET";
//api介面
$api = "https://api.weixin.qq.com/sns/jscode2session?appid={$appid}&secret={$secret}&js_code={$code}&grant_type=authorization_code";
//獲取GET請求
function httpGet($url){
    $curl = curl_init();
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($curl, CURLOPT_TIMEOUT, 500);
    curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, true);
    curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, true);
    curl_setopt($curl, CURLOPT_URL, $url);
    $res = curl_exec($curl);
    curl_close($curl);
    return $res;
}
//傳送
$str = httpGet($api);
echo $str;
?>