Google Calendar API - Freebusy

<?php
	
require_once 'vendor/autoload.php';  

$client = new Google_Client();
$client->setScopes('https://www.googleapis.com/auth/calendar');  
$client->addScope(Google_Service_Calendar::CALENDAR);
$client->setDeveloperKey("MEIN_API_KEY");  

$cal = new Google_Service_Calendar($client);
$calendarId = 'primary';  
$freebusy_req = new Google_Service_Calendar_FreeBusyRequest();
$freebusy_req->setTimeMin('2019-10-01T08:00:00.000-07:00');  
$freebusy_req->setTimeMax('2019-10-31T10:00:00.000-07:00');  
$freebusy_req->setTimeZone('Europe/Berlin');  
$freebusy_req->setCalendarExpansionMax(10);
$freebusy_req->setGroupExpansionMax(10);

$item = new Google_Service_Calendar_FreeBusyRequestItem();
$item->setId($calendarId);
$freebusy_req->setItems(array($item));
$query = $cal->freebusy->query($freebusy_req);

$response_calendar = $query->getCalendars();
$busy_obj = $response_calendar[$calendarId]->getBusy();


echo '<pre>';  
print_r($response_calendar);
echo '</pre>';  
	
?>

Array
(
    [primary] => Google_Service_Calendar_FreeBusyCalendar Object
        (
            [collection_key:protected] => errors
            [busyType:protected] => Google_Service_Calendar_TimePeriod
            [busyDataType:protected] => array
            [errorsType:protected] => Google_Service_Calendar_Error
            [errorsDataType:protected] => array
            [internal_gapi_mappings:protected] => Array
                (
                )

            [modelData:protected] => Array
                (
                )

            [processed:protected] => Array
                (
                )

            [errors] => Array
                (
                     => Google_Service_Calendar_Error Object
                        (
                            [domain] => global
                            [reason] => internalError
                            [internal_gapi_mappings:protected] => Array
                                (
                                )

                            [modelData:protected] => Array
                                (
                                )

                            [processed:protected] => Array
                                (
                                )

                        )

                )

            [busy] => Array
                (
                )

        )

)