<?php
use Microsoft\Graph\Beta\GraphServiceClient;
use Microsoft\Graph\Beta\Generated\Users\Item\OnlineMeetings\Item\Registration\RegistrationRequestBuilderGetRequestConfiguration;
$graphServiceClient = new GraphServiceClient($tokenRequestContext, $scopes);
$requestConfiguration = new RegistrationRequestBuilderGetRequestConfiguration();
$queryParameters = RegistrationRequestBuilderGetRequestConfiguration::createQueryParameters();
$queryParameters->expand = ["microsoft.graph.meetingRegistration/customQuestions"];
$requestConfiguration->queryParameters = $queryParameters;
$result = $graphServiceClient->me()->onlineMeetings()->byOnlineMeetingId('onlineMeeting-id')->registration()->get($requestConfiguration)->wait();