To create an ad group for your Smart Display campaign, follow the same process you use for other ad groups. However, since Google Ads manages most aspects of a Smart Display campaign, targeting options at the ad group level are not allowed.
PHP
private static function createAdGroup(
GoogleAdsClient $googleAdsClient,
int $customerId,
string $campaignResourceName
) {
// Constructs an ad group and set its type.
$adGroup = new AdGroup([
'name' => 'Earth to Mars Cruises #' . uniqid(),
'campaign' => $campaignResourceName,
'status' => AdGroupStatus::PAUSED,
]);
// Creates an ad group operation.
$adGroupOperation = new AdGroupOperation();
$adGroupOperation->setCreate($adGroup);
// Issues a mutate request to add the ad group.
$adGroupServiceClient = $googleAdsClient->getAdGroupServiceClient();
/** @var MutateAdGroupsResponse $adGroupResponse */
$adGroupResponse = $adGroupServiceClient->mutateAdGroups($customerId, [$adGroupOperation]);
// Print out some information about the added ad group.
$adGroupResourceName = $adGroupResponse->getResults()[0]->getResourceName();
printf("Added ad group named '%s'.%s", $adGroupResourceName, PHP_EOL);
return $adGroupResourceName;
}