php微信公众号code获取不到,微信公众号调取用户信息，遇到invalid code的问题

使用了php，php部分如下：

$code = $_GET["code"];

$userinfo = getUserInfo($code);

function getUserInfo($code)

{

$appid = "1111111111";

$appsecret = "1111111111111";//appid和appsecret在这里隐去，在源代码中是正确的

$access_token = "";

//Get access_token

$access_token_url = "https://api.weixin.qq.com/sns/oauth2/access_token?appid=$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'];

//Get user info

$userinfo_url = "https://api.weixin.qq.com/sns/userinfo?access_token=$