无法检索pagePathLevel1维度

I am trying to retrieve ga:pagePathLevel1 here but getting error

Warning: array_merge(): Argument #2 is not an array in ...\google-api-php-client\src\Google\Service\Analytics.php on line 1925

function getResults(&$analytics, $profileId) {
  // Calls the Core Reporting API and queries for the number of sessions
  // for the last seven days.
  $analytica_report['data_ga_get'] = $analytics->data_ga->get(
      'ga:' . $profileId,
      '7daysAgo',
      'today',
 'ga:sessions,ga:pageviews,ga:uniquePageviews,ga:bounces,ga:timeOnPage,ga:sessionDuration,ga:entrances,ga:exits,ga:searchUniques,ga:transactions',
     'ga:pagePathLevel1,ga:pagePathLevel2'      
      );

Can anybody suggest how I can make it correct ?

The last parameter in the method is optional parameters. Try something like this

$optParams = array(
      'dimensions' => 'ga:pagePathLevel1,ga:pagePathLevel2');

  return $service->data_ga->get(
      'ga:' . $profileId,
      '7daysAgo',
      'today',
      'ga:sessions,ga:pageviews,ga:uniquePageviews,ga:bounces,ga:timeOnPage,ga:sessionDuration,ga:entrances,ga:exits,ga:searchUniques,ga:transactions',
      $optParams);
}

You might also find the documentation useful.