# Subscriptions: Getting Started
Subscriptions allow GraphQL clients to observe specific events and receive updates from the server when those events occur.
NOTE
Much of the credit should be given to the Ruby implementation (opens new window) as they provided a great overview of how the backend should work.
# Setup
Install the Pusher PHP Library (opens new window) for interacting with the Pusher HTTP API.
composer require pusher/pusher-php-server
Add the service provider to your config/app.php
'providers' => [
\Nuwave\Lighthouse\Subscriptions\SubscriptionServiceProvider::class,
],