Google日历定期事件php API

Question

我已经尝试通过php api来获取日历事件，例如

           $service = new Google_Service_Calendar( $client );

            $arr_options = array(
                'singleEvents' => true,
            );

            $calendarId = 'primary';
            $results = $service->events->listEvents( $calendarId, 
             $arr_options );
             $events = $results->getItems();
               foreach( $events as $event ) {
               'title' => $event->getSummary(),
               recurrence=>$event->getrecurrence();
               }  

响应重复数组为空。

             0 => array:18 [▼
            "title" => "10th SEPTEMBER PROJECT DUPLICATE 1"  
            "recurrence" => null
            ]

下面是我的插入事件API

            $event = new Google_Service_Calendar_Event();
            $event->setSummary('Appointment');
           $event->setLocation('Somewhere');
             $start = new Google_Service_Calendar_EventDateTime();
            $start->setDateTime('2011-06-03T10:00:00.000-07:00');
             $start->setTimeZone('America/Los_Angeles');
          $event->setStart($start);
          $end = new Google_Service_Calendar_EventDateTime();
         $end->setDateTime('2011-06-03T10:25:00.000-07:00');
              $end->setTimeZone('America/Los_Angeles');
            $event->setEnd($end);
          $event- >setRecurrence(array('RRULE:FREQ=WEEKLY;UNTIL=20110701T170000Z'));

      $recurringEvent = $service->events->insert('primary', $event);

现在我需要将更新事件api与 复发

但是作为响应，重复数组为null。 请帮助我如何获取重复数组。