tasplanning_report/public/drive_quota.php

<?php
require __DIR__ . '/vendor/autoload.php';
$client = new Google\Client();
$client->useApplicationDefaultCredentials();
$client->setScopes([Google\Service\Drive::DRIVE]);
$drive = new Google\Service\Drive($client);
$about = $drive->about->get(['fields' => 'user, storageQuota']);
header('Content-Type: application/json');
echo json_encode($about, JSON_PRETTY_PRINT);