Firebase: Verifying ID tokens from the REST API

Job ID: 32145001

Budget: $15 – $25 USD

Consulting about how to Verify Firebase's ID token by using REST API.
I have to write PHP code that receive ID token (not Sign in) and prefer to do it with REST API.
The other option is installing Firebase Admin PHP SDK ($ composer require kreait/firebase-php) but I prefer not to use it, unless there is no choice.
The project is to guide me step by step, the best way to do it.
Related categories: PHP Android Google Firebase