function UpdateAd(AdWordsUser $user, $adGroupId, $adId) {
$adGroupAdService = $user->GetService('AdGroupAdService', ADWORDS_VERSION);
$ad = new TextAd();
$ad->id = $adId;
$ad->headline = 'Test Headline Text';
$ad->description1 = 'Updates description1 text';
// Create ad group ad.
$adGroupAd = new AdGroupAd();
$adGroupAd->adGroupId = $adGroupId;
$adGroupAd->ad = $ad;
// Update the status.
$adGroupAd->status = 'ENABLED';
// Create operation.
$operation = new AdGroupAdOperation();
$operation->operand = $adGroupAd;
$operation->operator = 'SET';
$operations = array($operation);
// Make the mutate request.
return $adGroupAdService->mutate($operations);
}