目前我正在尝试使用 Google Analytics Data API v1 从 GA4 获取 json 数据。但是，返回的响应不是纯 json 数据，相反，如果我只是使用 PHP 打印它，它会给我 {}。但是，使用预定义的方法，我们可以获得该值。请问，有没有办法得到纯json数据？

<?php
putenv('GOOGLE_APPLICATION_CREDENTIALS=xxx.json');

require_once 'vendorautoload.php';

use GoogleAnalyticsDataV1betaBetaAnalyticsDataClient;
use GoogleAnalyticsDataV1betaDateRange;
use GoogleAnalyticsDataV1betaDimension;
use GoogleAnalyticsDataV1betaMetric;
use GoogleCloudBigQueryConnectionRest;

$property_id = 'xxx'; // GA4 property ID

// Using a default constructor instructs the client to use the credentials
// specified in GOOGLE_APPLICATION_CREDENTIALS environment variable.
$client = new BetaAnalyticsDataClient();

// Make an API call.
$response = $client->runReport([
  'property' => 'properties/' . $property_id,
  'dateRanges' => [
    new DateRange([
      'start_date' => '2022-06-30',
      'end_date' => 'today',
    ]),
  ],
  'dimensions' => [
    new Dimension(
      [
        'name' => 'city',
      ]
    ),
  ],
  'metrics' => [
    new Metric(
      [
        'name' => 'activeUsers',
      ]
    )
  ]
]);

print 'Report result: ' . PHP_EOL;

printVisitorsLocationInNumber($response);

function printVisitorsLocationInNumber($resp) {
  foreach ($resp->getRows() as $row) {
    echo
    $row->getDimensionValues()[0]->getValue() . ' ' . $row->getMetricValues()[0]->getValue() . PHP_EOL . '</br>';;
  }
}