1.php

<?php

namespace Ololo\Bundle\UsersBundle\Service;

use Doctrine\ORM\EntityManager;

use Ololo\Bundle\UsersBundle\Entity\User;
use Ololo\Bundle\UsersBundle\Entity\Friendship;

use Ololo\Bundle\UsersBundle\Event\FriendshipSuccessEvent;

class FriendshipService
{
	protected $em;
	protected $dispatcher;

	public function __construct(EntityManager $em, $eventDispatcher)
	{
		$this->em = $em;
		$this->dispatcher = $eventDispatcher;
	}

	public function makeFriendship($user, $friend)
	{
		$user = $this->em->find('OloloUsersBundle:User', $user instanceof User ? $user->getId() : $user);
		if (!$user) {
			return array('status' => 'error', 'error' => 'OloloUsersBundle.friendship_service.base_user_not_exist');
		}

		$friend = $this->em->find('OloloUsersBundle:User', $friend instanceof User ? $friend->getId() : $friend);
		if (!$friend) {
			return array('status' => 'error', 'error' => 'OloloUsersBundle.friendship_service.friend_user_not_exist');
		}

		if ($friend->getId() == $user->getId()) {
			return array('status' => 'error', 'error' => 'OloloUsersBundle.friendship_service.friend_is_user');
		}
		
		$directFriendship = $this->em
			->createQuery('
				SELECT f
				FROM OloloUsersBundle:Friendship f
				WHERE f.user = :user AND f.friend = :friend
			')
			->setParameters(compact('user', 'friend'))
			->getOneOrNullResult();

		$inversedFriendship = $this->em
			->createQuery('
				SELECT f
				FROM OloloUsersBundle:Friendship f
				WHERE f.user = :friend AND f.friend = :user
			')
			->setParameters(compact('user', 'friend'))
			->getOneOrNullResult();

		if ($directFriendship) {
			return array('status' => 'error', 'error' => 'OloloUsersBundle.friendship_service.already_friendly');
		}

		$friendship = new Friendship();
		$friendship->setFriend($friend);
		$friendship->setUser($user);

		if ($inversedFriendship) { // I'm already in his friends. Confirm friendship
			$friendship->setMutual(true);
			$inversedFriendship->setMutual(true);

			//TODO: call after flushing
			$event = new FriendshipSuccessEvent();
			$event->setBaseUser($user);
			$event->setFriend($friend);
			$this->eventDispatcher->dispatch($event);
		}

		$this->em->persist($friendship);
		$this->em->flush();
		
		return array('status' => 'success');
	}

	public function removeFriendship($user, $friend)
	{
		throw new \BadMethodCallException('Not implimented yet');
	}
}

2.php

<?php
// example of controller

if (!$this->getAuth()->isAuthenticated()) {
	throw $this->createAccessDinedException($this->trans('OloloUsersBundle.not_authenticated'));
}

$service = new FriendshipService($this->getEntityManager('write'), $this->getEventDispatcher());
$response = $service->makeFriendship($this->getAuth()->getId(), $this->getQueryParam('friend'));

return $this->render($template, $response);