use Symfony\Component\DependencyInjection\ContainerInterface; class MyService { private $container; public function __construct(ContainerInterface $container) { $this->container = $container; } public function someMethod() { $mailer = $this->container->get('mailer'); $mailer->send(...); } }In this code example, the `MyService` class depends on the `mailer` service, which is defined in the container. The service is retrieved from the container in the `someMethod()` method. The Symfony\Component\DependencyInjection\ContainerInterface is part of the Symfony Dependency Injection component, which is a package library for managing dependencies and services in PHP applications.