谷歌上的身份验证：OAuth2不断返回“invalid_grant”

我开始在我的新应用程序上配置谷歌日历。我几乎制作了谷歌开发人员显示的身份验证代码的精确副本（https://developers.google.com/google-apps/calendar/instantiate），但我一直得到以下错误：

提取 OAuth2 访问令牌时出错，消息：“invalid_grant”

我目前正在使用Fork-CMS（http://www.fork-cms.com），一个年轻的lightweigth CMS。我正确地配置了google-api-php-client的config.php文件。（client-id， client-secret， redirect-uri， development key,...）并且重定向 uri 已在 google api 的控制台上正确设置。我的代码如下所示：

<?php

/**
* This is a widget with a calendar implementation.
*
* @package       frontend
* @subpackage    events
*
* @author        Michiel Vlaminck <michielvlaminck@gmail.com>
*/
class FrontendEventsWidgetCalendar extends FrontendBaseWidget
{

    private $events = array();
    private $authUrl = array();

    /**
    * Execute the extra
    *
    * @return    void
    */
    public function execute()
    {      
        // call parent
        parent::execute();

        // load template
        $this->loadTemplate();

        // get data
        $this->getData();

        // parse
        $this->parse();
    }


    /**
    * Get the data from Google Calendar
    * This method is only executed if the template isn't cached
    *
    * @return    void
    */
    private function getData()
    {
        require_once PATH_LIBRARY . '/external/google-api-php-client/src/apiClient.php';
        require_once PATH_LIBRARY . '/external/google-api-php-client/src/contrib/apiCalendarService.php';

        $client = new apiClient();

        $service = new apiCalendarService($client);

        if (isset($_SESSION['oauth_access_token'])) {
            $client->setAccessToken($_SESSION['oauth_access_token']);
        } else {
            $token = $client->authenticate();
            $_SESSION['oauth_access_token'] = $token;
        }

        if ($client->getAccessToken()) {

            $calId = FrontendEventsModel::getCalendarId((int) $this->data['id']);
            $calId = $calId[0]['calendar_id'];

            $events = $service->events->listEvents($calId);
            $this->events = $events['items'];

            $_SESSION['oauth_access_token'] = $client->getAccessToken();

        } else {
            $this->authUrl = $client->createAuthUrl();
        }
    }


    /**
    * Parse
    *
    * @return    void
    */
    private function parse()
    {
        $this->tpl->assign('events', $this->events);
        $this->tpl->assign('authUrl', $this->authUrl);
    }
}

?>

当我第一次打开这个小部件页面时，我被定向到谷歌来验证应用程序。当我同意时，我被重定向到我的应用程序，这就是我得到的点：

apiAuthException » Main

Message Error fetching OAuth2 access token, message: 'invalid_grant'
File    C:\wamp\www\Officevibes\library/external\google-api-php-client\src\auth\apiOAuth2.php
Line    105
Date    Thu, 05 Apr 2012 08:34:47 +0000
URL http://localhost/calendar?code=4/YPUpFklKvhEeTcMm4moRth3x49oe
Referring URL   (Unknown)
Request Method  GET
User-agent  Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.19 (KHTML, like Gecko) Chrome/18.0.1025.142 Safari/535.19