if(isset($_SESSION['user'])){
              print_r($_SESSION['user']);
              exit;
            }

$appid='wx1d7c6fcd6131143b3';

            $redirect_url="http://www.antfortune.vip/callback.php";
            $scope='snsapi_userinfo';//获取的方式;


            $url='https://open.weixin.qq.com/connect/oauth2/authorize"Location：".$url);

getOpenid.php



<"your appid";
$appsecret="your appsecret";
$code=$_GET['code'];



function getOpenID($appid,$appsecret,$code){
$url="https://api.weixin.qq.com/sns/oauth2/access_token".$appid."&secret=". 
$appsecret."&code=".$code."&grant_type=authorization_code";

$weixin=file_get_contents($url);//通过code换取网页授权access_token
$jsondecode=json_decode($weixin); //对JSON格式的字符串进行编码
$array = get_object_vars($jsondecode);//转换成数组
$openid = $array['openid'];//输出openid
return $openid;
}

echo getOpenID($appid,$appsecret,$code);