The Verify Phone API lets you send a 6 digits code to a user's phone and validate that they received it. Verify Phone can be used for anti-fraud purposes, such as validating users phone and 2-factor authentication.
Using with Composer
composer require twilio/sdk
In this case, you would include composer's auto-loader at the top of your source files:
<?php
require __DIR__ . '/vendor/autoload.php';