<?php
use Microsoft\Graph\Beta\GraphServiceClient;
use Microsoft\Graph\Beta\Generated\Models\Application;
use Microsoft\Graph\Beta\Generated\Models\UnrestrictedAudience;
$graphServiceClient = new GraphServiceClient($tokenRequestContext, $scopes);
$requestBody = new Application();
$requestBody->setSignInAudience('AzureADMyOrg');
$signInAudienceRestrictions = new UnrestrictedAudience();
$signInAudienceRestrictions->setOdataType('#microsoft.graph.unrestrictedAudience');
$requestBody->setSignInAudienceRestrictions($signInAudienceRestrictions);
$result = $graphServiceClient->applications()->byApplicationId('application-id')->patch($requestBody)->wait();