<?php
use Microsoft\Graph\GraphServiceClient;
use Microsoft\Graph\Generated\Users\Item\Events\Item\TentativelyAccept\TentativelyAcceptPostRequestBody;
use Microsoft\Graph\Generated\Models\TimeSlot;
use Microsoft\Graph\Generated\Models\DateTimeTimeZone;
$graphServiceClient = new GraphServiceClient($tokenRequestContext, $scopes);
$requestBody = new TentativelyAcceptPostRequestBody();
$requestBody->setComment('I may not be able to make this week. How about next week?');
$requestBody->setSendResponse(true);
$proposedNewTime = new TimeSlot();
$proposedNewTimeStart = new DateTimeTimeZone();
$proposedNewTimeStart->setDateTime('2019-12-02T18:00:00');
$proposedNewTimeStart->setTimeZone('Pacific Standard Time');
$proposedNewTime->setStart($proposedNewTimeStart);
$proposedNewTimeEnd = new DateTimeTimeZone();
$proposedNewTimeEnd->setDateTime('2019-12-02T19:00:00');
$proposedNewTimeEnd->setTimeZone('Pacific Standard Time');
$proposedNewTime->setEnd($proposedNewTimeEnd);
$requestBody->setProposedNewTime($proposedNewTime);
$graphServiceClient->me()->events()->byEventId('event-id')->tentativelyAccept()->post($requestBody)->wait();