<?php
use Microsoft\Graph\Beta\GraphServiceClient;
use Microsoft\Graph\Beta\Generated\Models\Ediscovery\UserSource;
$graphServiceClient = new GraphServiceClient($tokenRequestContext, $scopes);
$requestBody = new UserSource();
$requestBody->setOdataType('microsoft.graph.ediscovery.userSource');
$requestBody->setEmail('badguy@contoso.com');
$result = $graphServiceClient->compliance()->ediscovery()->cases()->byCaseId('case-id')->sourceCollections()->bySourceCollectionId('sourceCollection-id')->additionalSources()->post($requestBody)->wait();