<?php
use Microsoft\Graph\Beta\GraphServiceClient;
use Microsoft\Graph\Beta\Generated\Models\MeetingRegistrant;
use Microsoft\Graph\Beta\Generated\Models\CustomQuestionAnswer;
$graphServiceClient = new GraphServiceClient($tokenRequestContext, $scopes);
$requestBody = new MeetingRegistrant();
$requestBody->setOdataType('#microsoft.graph.meetingRegistrant');
$requestBody->setFirstName('Lisa');
$requestBody->setLastName('Adkins');
$requestBody->setEmail('lisa.adkins@contoso.com');
$customQuestionAnswersCustomQuestionAnswer1 = new CustomQuestionAnswer();
$customQuestionAnswersCustomQuestionAnswer1->setQuestionId('MSM5YjlmM2Q4ZS03ZmVkLTRmN3gwMDIw94MDAyMF9hX3gwMDIwX2RldmU=');
$customQuestionAnswersCustomQuestionAnswer1->setValue('No');
$customQuestionAnswersArray []= $customQuestionAnswersCustomQuestionAnswer1;
$customQuestionAnswersCustomQuestionAnswer2 = new CustomQuestionAnswer();
$customQuestionAnswersCustomQuestionAnswer2->setQuestionId('MSM5M2E2OWQ1Ni1jZTc4LTQDAwMjBfZGlkX3gwMDIwX3lvdV94MDAyMF8=');
$customQuestionAnswersCustomQuestionAnswer2->setValue('Internet');
$customQuestionAnswersArray []= $customQuestionAnswersCustomQuestionAnswer2;
$requestBody->setCustomQuestionAnswers($customQuestionAnswersArray);
$result = $graphServiceClient->users()->byUserId('user-id')->onlineMeetings()->byOnlineMeetingId('onlineMeeting-id')->registration()->registrants()->post($requestBody)->wait();