How to use Google Sheets as a Database for your PHP App

The tutorial demonstrates how to use Google Sheets as a database for a PHP application, specifically with Order Desk's API and Twilio's SMS service. It covers the setup of environment variables, authentication with Google and Twilio, and the creation of clients for Order Desk and Google Sheets. The `Order` class is used to fetch data from Order Desk, update Google Sheets, and send a confirmation SMS using Twilio. The application uses dependency injection to create objects and can be improved by setting up a cron job to check for orders at given intervals.