"；致命错误:类'；Google_Http_Request'；在“；同时使用Oauth2.0身份验证

我正在尝试使用Google Contact API检索我的所有联系人。为此，我使用了Oauth2.0身份验证和Google Contact API For PHP。

但我得到了这个错误："致命错误：在"中找不到类"Google_Http_Request"

找不到原因。我甚至使用了Google_HttpRequest，但错误保持不变，但这次是针对"Google_HttpRequest"。

使用的代码如下，有人能帮上忙吗？因为这在互联网上没有可用的帮助

<?php
//require_once 'C:/xampp/htdocs/google-api-php-client-master/src/Google/Client.php';
require_once 'C:/xampp/htdocs/google-api-php-client-master/vendor/autoload.php';// or wherever autoload.php is located
session_start();
//Declare your Google Client ID, Google Client secret and Google redirect uri in  php variables
$google_client_id = 'xxx-yyy.apps.googleusercontent.com';
$google_client_secret = 'xxxx';
$google_redirect_uri = 'https://localhost:4433/xxx.php';
$client = new Google_Client();
$client -> setApplicationName('My application name');
$client -> setClientid($google_client_id);
$client -> setClientSecret($google_client_secret);
$client -> setRedirectUri($google_redirect_uri);
$client -> setAccessType('online');
$client->setApplicationName('Google Contacts PHP Sample');
$client->setScopes("http://www.google.com/m8/feeds/");
///if (isset($_GET['code'])) {
/// $client->authenticate($_GET['code']);
/// $auth_code = $_GET["code"];
/// $_SESSION['google_code'] = $auth_code;
/// header('Location: ' . $google_redirect_uri);
///}
if (isset($_GET['code'])) {
$client->authenticate($_GET['code']);
$_SESSION['token'] = $client->getAccessToken();
$redirect = 'http://' . $_SERVER['HTTP_HOST'] . $_SERVER['PHP_SELF'];
header('Location: ' . filter_var($redirect, FILTER_SANITIZE_URL));
}
if (isset($_SESSION['token'])) {
$client->setAccessToken($_SESSION['token']);
}
if (isset($_REQUEST['logout'])) {
unset($_SESSION['token']);
$client->revokeToken();
}
if ($client->getAccessToken()) {
//$req = new Google_Http_Request("https://www.google.com/m8/feeds/contacts/default/full", 'GET', null, null);   
$req = new Google_Http_Request("https://www.google.com/m8/feeds/contacts/default/full");
$val = $client->getIo()->authenticatedRequest($req);

// The contacts api only returns XML responses.
$response = json_encode(simplexml_load_string($val->getResponseBody()));
print "<pre>" . print_r(json_decode($response, true), true) . "</pre>";
// The access token may have been updated lazily.
$_SESSION['token'] = $client->getAccessToken();
} else {
$auth = $client->createAuthUrl();
}
if (isset($auth)) {
print "<a class=login href='$auth'>Connect Me!</a>";
} else {
print "<a class=logout href='?logout'>Logout</a>";
}