使用带有PHP的Google身份验证API

下面的代码不是打印userinfo，而是打印Google授予的访问令牌的详细信息。代码很简单，但我无法找出的确切原因

    <?php
$url = 'https://accounts.google.com/o/oauth2/token';
$fields = array(
        'code'=>urlencode($_GET['code']),
        'client_id'=>urlencode('###########.apps.googleusercontent.com'),
        'client_secret'=>urlencode('###########'),
        'redirect_uri'=>urlencode('http://######odie.co.in/googlogin'),
        'grant_type'=>urlencode('authorization_code'),
                    );

foreach($fields as $key=>$value) {
     $fields_string .= $key.'='.$value.'&';
     }
rtrim($fields_string,'&');
//open connection
$ch = curl_init();
//set the url, number of POST vars, POST data
curl_setopt($ch,CURLOPT_URL,$url);
curl_setopt($ch,CURLOPT_POST,count($fields));
curl_setopt($ch,CURLOPT_POSTFIELDS,$fields_string);
//execute post
$result = curl_exec($ch);

//close connection
curl_close($ch);
$data =  json_decode($result);
print_r(file_get_contents(' https://www.googleapis.com/oauth2/v1/userinfo?access_token='.$data['access_token']));
?>