<?php
use Microsoft\Graph\GraphServiceClient;
use Microsoft\Graph\Generated\Models\GroupSetting;
use Microsoft\Graph\Generated\Models\SettingValue;
$graphServiceClient = new GraphServiceClient($tokenRequestContext, $scopes);
$requestBody = new GroupSetting();
$valuesSettingValue1 = new SettingValue();
$valuesSettingValue1->setName('AllowToAddGuests');
$valuesSettingValue1->setValue('true');
$valuesArray []= $valuesSettingValue1;
$requestBody->setValues($valuesArray);
$result = $graphServiceClient->groups()->byGroupId('group-id')->settings()->byGroupSettingId('groupSetting-id')->patch($requestBody)->wait();