<?php
//回调地址中获取code，拿到code后在去请求一个接口获取access_token和openid
$code = $_GET["code"];

//当前回调地址(当前的页面地址)
$url = 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];
if ($code == '') {
    oauth1($url);
}

function oauth1($url)
{
    // 跳转微信提供的地址获取code
    $appid = "你的appid";
    
    $redirect_uri = urlencode($url);
    header("Location: https://open.weixin.qq.com/connect/oauth2/authorize?appid={$appid}&redirect_uri={$redirect_uri}&response_type=code&scope=snsapi_base&state=123#wechat_redirect");
}

//根据code获取openid
function get_user_openid1($code)
{
    $appid = "你的appid";
    $appsecret = "你的appsecret";

    $access_token_url = "https://api.weixin.qq.com/sns/oauth2/access_token?appid={$appid}&secret={$appsecret}&code={$code}&grant_type=authorization_code";
    $access_token_json = https_request($access_token_url);
    $access_token_array = json_decode($access_token_json, true);
    $access_token=$access_token_array['access_token'];
    $openid = $access_token_array['openid'];
    return $openid;
}

function https_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($curl, CURLOPT_POST, 1);
        curl_setopt($curl, CURLOPT_POSTFIELDS, $data);
    }
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
    $output = curl_exec($curl);
    curl_close($curl);
    return $output;
}


// 用户的openid
echo "openid:" . get_user_openid1($code);