title: Google OAuth 2.0 Service Account Authentication
body: <p>How Google Service Account can be authenticated using PHP?
  Here are the references-
  1. <a href="https://developers.google.com/api-client-library/php/guide/aaa_oauth2_service" rel="nofollow">https://developers.google.com/api-client-library/php/guide/aaa_oauth2_service</a>
  2. <a href="https://github.com/google/google-api-php-client/blob/master/examples/service-account.php" rel="nofollow">https://github.com/google/google-api-php-client/blob/master/examples/service-account.php</a></p>