Simple example demonstrating Google Calendar API using Google's PHP client library.

*To run*:
 - `composer install`
 - Drop in your own `client_secrets.json` file.
 - `php -S localhost:8080`
 - Browse to `http://localhost:8080`

Sources:
 - https://developers.google.com/api-client-library/php/auth/web-app#protectauthcode
 - https://developers.google.com/google-apps/calendar/quickstart/php

