Google oauth2不返回id_token

我似乎怀念oauth2。我得到了，access_token但没有id_token！

我通过传递以下内容授予我的“代码”，使用以下代码来获取google access_token： https://accounts.google.com/o/oauth2/auth

$oauth2token_url = "https://accounts.google.com/o/oauth2/token";
$clienttoken_post = array(
    "code" => $code,
    "client_id" => $client_id,
    "client_secret" => $client_secret,
    "redirect_uri" => $redirect_uri,
    "grant_type" => "authorization_code"
);

$curl = curl_init($oauth2token_url);

curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_POSTFIELDS, $clienttoken_post);
curl_setopt($curl, CURLOPT_HTTPAUTH, CURLAUTH_ANY);
curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);

$json_response = curl_exec($curl);
curl_close($curl);
var_dump($json_response);

一切似乎都工作，但根据谷歌的文档https://developers.google.com/accounts/docs/OAuth2Login#exchangecode我应该得到access_token, id_token, expires_in, token_type我做除id_token

var_dump($json_response); 显示以下内容：

string(126) "{ "access_token" : "ya29.AHES6ZSGlHVW9qA23xs8bHBP578Ef8S5cntJIcPT_SHWA", "token_type" : "Bearer", "expires_in" : 3598 }

我在这里想念什么？