1、配置授权回调页面域名，如 www.aaa.com

2、模拟公众号的第三方网页，fn_system.php

<?php

if(empty($_SESSION[‘user‘])){
	
	header("Location:http://www.aaa.net/uc/fn_wx_login.php");
}else{
	print_r($_SESSION[‘user‘]);
}

?>

3、访问第三方网页时，如果检查session中不存在会话信息，则跳转至登陆页，fn_wx_login.php

<?php

	$appid = "公众号在微信的appid";
	$url = ‘https://open.weixin.qq.com/connect/oauth2/authorize?appid=‘.$appid.‘&redirect_uri=http%3a%2f%2fwww.aaa.com%2fuc%2ffn_callback.php&response_type=code&scope=snsapi_userinfo&state=STATE#wechat_redirect‘;
	header("Location:".$url);

?>

4、在登陆页组装appid，回跳url等信息，然后跳转至微信的用户授权页。

5、在微信的用户授权页，如果用户选择了“同意授权”，则微信重新回跳至第三方网页的回跳地址时，会附带上code参数。

6、第三方网页的回跳url中，首先从请求中取得code，然后根据code进一步换取openid和access_token，然后就可以根据openid和access_token调用微信的相关接口查询用户信息了。

<?php

$appid = "公众号在微信的appid";
$secret = "公众号在微信的app secret";
$code = $_GET["code"];
$get_token_url = ‘https://api.weixin.qq.com/sns/oauth2/access_token?appid=‘.$appid.‘&secret=‘.$secret.‘&code=‘.$code.‘&grant_type=authorization_code‘;

$ch = curl_init();
curl_setopt($ch,CURLOPT_URL,$get_token_url);
curl_setopt($ch,CURLOPT_HEADER,0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1 );
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 10);
$res = curl_exec($ch);
curl_close($ch);
$json_obj = json_decode($res,true);

//根据openid和access_token查询用户信息
$access_token = $json_obj[‘access_token‘];
$openid = $json_obj[‘openid‘];
$get_user_info_url = ‘https://api.weixin.qq.com/sns/userinfo?access_token=‘.$access_token.‘&openid=‘.$openid.‘&lang=zh_CN‘;

$ch = curl_init();
curl_setopt($ch,CURLOPT_URL,$get_user_info_url);
curl_setopt($ch,CURLOPT_HEADER,0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1 );
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 10);
$res = curl_exec($ch);
curl_close($ch);

//解析json
$user_obj = json_decode($res,true);
$_SESSION[‘user‘] = $user_obj;
print_r($user_obj);

?>