Google calendar event invite notifications send using google api php library is not working

[jitendr...@isol.co.in]

I am using below code which create an event successfully in calendar but not sending invite notification to guests Plz help me

            $event = new Google_Event();
            $event->setSummary($_REQUEST['

summary']);
            $event->setLocation($_REQUEST['location']);
            $start = new Google_EventDateTime();
            $start->setDateTime($start_date);
            $event->setStart($start);
            $end = new Google_EventDateTime();
            $end->setDateTime($end_date);
            $event->setEnd($end);
            $event->sendNotifications=true;
            $attendee1 = new Google_EventAttendee();
            $attendee1->setEmail('myemail');
            $attendee2 = new Google_EventAttendee();
           $attendee2->setEmail('secondemail');
           $attendee3 = new Google_EventAttendee();
           $attendee3->setEmail('thirdemail');
            // ...
            $attendees = array($attendee1,$attendee2,$attendee3);
            $event->attendees = $attendees;
            $createdEvent = $cal->events->insert('********calendar id***********', $event);