The Twilio API is adding support for WhatsApp messaging, allowing developers to send and receive messages on the platform. The Twilio API Sandbox provides a testing environment where developers can experiment with this new feature using PHP. To get started, developers need to set up their project with Composer, install the Twilio SDK, and link their personal WhatsApp account to the sandbox. They can then use templates or create interactive scripts to send messages, including a simple game-like interaction where the recipient tries to guess a number between 1 and 5. The process involves creating PHP scripts that interact with the Twilio API, using environment variables to store sensitive information such as account credentials. Once the script is complete, it can be deployed through a public URL, using ngrok to create a secure connection. With this new feature, developers can expand their reach and engage with users on WhatsApp.