/**
 * Runs the example.
 * @param string $clientId the OAuth2 client ID
 * @param string $clientSecret the OAuth2 client secret
 */
function UseOAuth2Example($clientId, $clientSecret)
{
    // Set the OAuth2 client ID and secret.
    $oauth2Info = array('client_id' => $clientId, 'client_secret' => $clientSecret);
    // Create the AdWordsUser and set the OAuth2 info.
    $user = new AdWordsUser();
    $user->SetOAuth2Info($oauth2Info);
    $user->LogAll();
    // Get the authorization URL for the OAuth2 token.
    // No redirect URL is being used since this is an installed application. A web
    // application would pass in a redirect URL back to the application,
    // ensuring it's one that has been configured in the API console.
    // Passing true for the second parameter ($offline) will provide us a refresh
    // token which can used be refresh the access token when it expires.
    $authorizationUrl = $user->GetOAuth2AuthorizationUrl(NULL, TRUE);
    // In a web application you would redirect the user to the authorization URL
    // and after approving the token they would be redirected back to the
    // redirect URL, with the URL parameter "code" added. For desktop
    // or server applications, spawn a browser to the URL and then have the user
    // enter the authorization code that is displayed.
    printf("Log in to your AdWords account and open the following URL: %s\n", $authorizationUrl);
    print 'After approving the token enter the authorization code here: ';
    $stdin = fopen('php://stdin', 'r');
    $code = trim(fgets($stdin));
    fclose($stdin);
    // Get the access token using the authorization code. Ensure you use the same
    // redirect URL used when requesting authorization.
    $user->GetOAuth2AccessToken($code, NULL);
    // The access token expires but the refresh token obtained for offline use
    // doesn't, and should be stored for later use.
    $oauth2Info = $user->GetOAuth2Info();
    print "OAuth2 authorization successful.\n";
    print_r($oauth2Info);
    // Get the number of campaigns in the account.
    $campaignService = $user->GetService('CampaignService', ADWORDS_VERSION);
    $selector = new Selector();
    $selector->fields = array('Id');
    $selector->paging = new Paging(0, 0);
    $page = $campaignService->get($selector);
    // Display number of campaigns.
    printf("Found %d campaigns.\n", $page->totalNumEntries);
}