在 Google Ads API 中，更新作業會使用欄位遮罩。欄位遮罩會列出您打算透過更新變更的所有欄位，而任何不在欄位遮罩中的指定欄位都會遭到忽略，即使已傳送至伺服器也一樣。您可以手動建立欄位遮罩，方法是建立 Google\Protobuf\FieldMask，製作一個陣列，並在其中填入您要變更的所有欄位名稱，然後將該陣列指派給欄位遮罩的路徑欄位。
您也可以使用內建的欄位遮罩公用程式 (FieldMasks)，這個公用程式會隱藏許多特定詳細資料，並監控您對實體欄位所做的變更，自動產生欄位遮罩。
以下是更新廣告活動的範例：
$campaign = new Campaign([
'resource_name' => ResourceNames::forCampaign($customerId, $campaignId),
'status' => CampaignStatus::PAUSED
]);
$campaignOperation = new CampaignOperation();
$campaignOperation->setUpdate($campaign);
$campaignOperation->setUpdateMask(FieldMasks::allSetFieldsOf($campaign));
這個程式碼會先建立 Campaign 物件，然後使用 ResourceNames 設定其資源名稱，讓 API 知道要更新哪個廣告活動。status 也設為 PAUSED。
程式碼接著會建立 CampaignOperation 物件，並將先前建立的廣告活動設為該物件。接著，系統會使用 FieldMasks::allSetFieldsOf() 為廣告活動建立欄位遮罩，並使用所有已變更的欄位。最後，它會將傳回的遮罩傳遞至廣告活動作業物件。
請注意，FieldMasks::allSetFieldsOf 是 FieldMasks::compare() 的方便方法。它會將傳入的物件與相同類別的空物件進行比較。舉例來說，在先前的程式碼中，您可以使用 FieldMasks::compare(new
Campaign(), $campaign) 而非 allSetFieldsOf()。
更新訊息欄位及其子欄位
MESSAGE 欄位可以有子欄位 (例如 MaximizeConversions，其中有三個：target_cpa_micros、cpc_bid_ceiling_micros 和 cpc_bid_floor_micros)，也可以完全沒有子欄位 (例如 ManualCpm)。
未定義子欄位的訊息欄位
更新未定義任何子欄位的 MESSAGE 欄位時，請使用 FieldMasks 產生欄位遮罩，如前文所述。
訊息欄位及其定義的子欄位
更新使用子欄位定義的 MESSAGE 欄位，但未明確設定該訊息的任何子欄位時，您必須手動將每個可變更的 MESSAGE 子欄位新增至 FieldMask，類似於前一個範例中從頭建立欄位遮罩。
一個常見的例子是更新廣告活動的出價策略，但未在新的出價策略中設定任何欄位。以下程式碼示範如何更新廣告活動，以便使用 MaximizeConversions 出價策略，且不設定出價策略的任何子欄位。
在這種情況下，使用 FieldMasks 的 allSetFieldsOf() 和 compare() 方法無法達成預期目標。
以下程式碼會產生包含 maximize_conversions 的欄位遮罩。不過，Google Ads API 不允許這種行為，以免誤刪欄位並產生 FieldMaskError.FIELD_HAS_SUBFIELDS 錯誤。
// Creates a campaign with the proper resource name and an empty
// MaximizeConversions field.
$campaign = new Campaign([
'resource_name' => ResourceNames::forCampaign($customerId, $campaignId),
'maximize_conversions' => new MaximizeConversions()
]);
// Constructs an operation, using the FieldMasks' allSetFieldsOf utility to
// derive the update mask. The field mask will include 'maximize_conversions`,
// which will produce a FieldMaskError.FIELD_HAS_SUBFIELDS error.
$campaignOperation = new CampaignOperation();
$campaignOperation->setUpdate($campaign);
$campaignOperation->setUpdateMask(FieldMasks::allSetFieldsOf($campaign));
// Sends the operation in a mutate request that will result in a
// FieldMaskError.FIELD_HAS_SUBFIELDS error because empty MESSAGE fields cannot
// be included in a field mask.
$campaignServiceClient = $googleAdsClient->getCampaignServiceClient();
$response = $campaignServiceClient->mutateCampaigns($customerId, [$campaignOperation]);
下列程式碼示範如何正確更新廣告活動，以便使用 MaximizeConversions 出價策略，且不設定任何子欄位。
// Creates a Campaign object with the proper resource name.
$campaign = new Campaign([
'resource_name' => ResourceNames::forCampaign($customerId, $campaignId)
]);
// Creates a field mask from the existing campaign and adds all of the mutable
// fields (only one in this case) on the MaximizeConversions bidding strategy to
// the field mask. Because this field is included in the field mask but
// excluded from the campaign object, the Google Ads API will set the campaign's
// bidding strategy to a MaximizeConversions object without any of its subfields
// set.
fieldMask = FieldMasks::allSetFieldsOf($campaign);
// Only include 'maximize_conversions.target_cpa_micros' in the field mask
// as it is the only mutable subfield on MaximizeConversions when used as a
// standard bidding strategy.
//
// Learn more about standard and portfolio bidding strategies here:
// https://developers.google.com/google-ads/api/docs/campaigns/bidding/assign-strategies
$fieldMask->setPaths(array_merge(
iterator_to_array($fieldMask->getPaths()->getIterator()),
['maximize_conversions.target_cpa_micros']
));
// Creates an operation to update the campaign with the specified fields.
$campaignOperation = new CampaignOperation();
$campaignOperation->setUpdate($campaign);
$campaignOperation->setUpdateMask($fieldMask);
清除欄位
部分欄位可明確清除。與先前的範例類似，您必須明確將這些欄位新增至欄位遮罩。舉例來說，假設您有一個使用 MaximizeConversions 出價策略的廣告活動，且 target_cpa_micros 欄位已設為大於 0 的值。
以下程式碼會執行，但 maximize_conversions.target_cpa_micros 不會新增至欄位遮罩，因此不會變更 target_cpa_micros 欄位：
// Creates a campaign with the proper resource name and a MaximizeConversions
// object with target_cpa_micros set to 0.
$campaign = new Campaign([
'resource_name' => ResourceNames::forCampaign($customerId, $campaignId),
'maximize_conversions' => new MaximizeConversions(['target_cpa' => 0]),
'status' => CampaignStatus::PAUSED
]);
// Constructs an operation, using the FieldMasks' allSetFieldsOf utility to
// derive the update mask. However, the field mask will NOT include
// 'maximize_conversions.target_cpa_micros'.
$campaignOperation = new CampaignOperation();
$campaignOperation->setUpdate($campaign);
$campaignOperation->setUpdateMask(FieldMasks::allSetFieldsOf($campaign));
// Sends the operation in a mutate request that will succeed but will NOT update
// the 'target_cpa_micros' field because
// 'maximize_conversions.target_cpa_micros' was not included in the field mask.
$campaignServiceClient = $googleAdsClient->getCampaignServiceClient();
$response = $campaignServiceClient->mutateCampaigns($customerId, [$campaignOperation]);
以下程式碼示範如何正確清除 MaximizeConversions 出價策略的 target_cpa_micros 欄位。
// Creates a Campaign object with the proper resource name.
$campaign = new Campaign([
'resource_name' => ResourceNames::forCampaign($customerId, $campaignId)
]);
// Constructs a field mask from the existing campaign and adds the
// 'maximize_conversions.target_cpa_micros' field to the field mask, which will
// clear this field from the bidding strategy without impacting any other fields
// on the bidding strategy.
$fieldMask = FieldMasks::allSetFieldsOf($campaign);
$fieldMask->setPaths(array_merge(
iterator_to_array($fieldMask->getPaths()->getIterator()),
['maximize_conversions.target_cpa_micros']
));
// Creates an operation to update the campaign with the specified field.
$campaignOperation = new CampaignOperation();
$campaignOperation->setUpdate($campaign);
$campaignOperation->setUpdateMask($fieldMask);
請注意，「不正確」的程式碼在 Google Ads API protocol buffers 中定義為 optional 的欄位上確實能正常運作。不過，由於 target_cpa_micros 並非 optional 欄位，因此「錯誤」程式碼不會更新出價策略來清除 target_cpa 欄位。