Bare Bones Google OAuth

google-oauth2.php

<?php

// composer require google/apiclient:^2.0
require_once __DIR__.'/vendor/autoload.php';

const CLIENT_ID = '';
const CLIENT_SECRET = '';
const APPLICATION_NAME = "";
const REDIRECT_URI = "http://localhost:8080/";
 
// Create API Client
$client = new Google_Client();
$client->setApplicationName(APPLICATION_NAME);
$client->setClientId(CLIENT_ID);
$client->setClientSecret(CLIENT_SECRET);
$client->setRedirectUri(REDIRECT_URI);
$client->addScope("https://www.googleapis.com/auth/userinfo.profile");
$client->addScope("https://www.googleapis.com/auth/userinfo.email");

$oauth = new Google_Service_Oauth2($client);

// Get code from login flow and set access token
if (isset($_GET['code'])) {
  $client->authenticate($_GET['code']);
  $client->setAccessToken($client->getAccessToken());
}

if ($client->getAccessToken()) {
  $userData = $oauth->userinfo->get();
  if(!empty($userData)) {
    header('Content-Type: application/json');
    echo(json_encode($userData, JSON_PRETTY_PRINT));
    $client->revokeToken();
  }
} else {
  $authUrl = $client->createAuthUrl();
  echo('<a href="'.$authUrl.'">Login</a>');
}