Cloud Datastore Client - Class AggregationQueryResult (1.33.1)

 use Google\Cloud\Datastore\DatastoreClient;

$datastore = new DatastoreClient();

$query = $datastore->AggregationQuery();
$query->kind('Companies');
$query->filter('companyName', '=', 'Google');
$query->limit(100);
$query->addAggregation(Aggregation::count()->alias('total_upto_100'));

$res = $datastore->runAggregationQuery($query);
echo $res->get('total_upto_100'); 

 $query = $datastore->AggregationQuery();
$query->kind('Companies');
$query->filter('companyName', '=', 'Google');
$query->addAggregation(Aggregation::count()->alias('total'));
$res = $client->runAggregationQuery($query);
echo $res->get('total');