DoctrineSomeRepository.php

<?php

namespace L3l0\Bundle\SomethingBundle\Repository;

use L3l0\Something\Model\Some;
use L3l0\Something\Repository\SomeRepository;
use Doctrine\Common\Persistence\ObjectManager;

class DoctrineSomeRepository implements SomeRepository
{
    private $manager;

    public function __construct(ObjectManager $manager)
    {
        $this->manager = $manager;
    }

    public function save(Some $some)
    {
        $this->manager->persist($some);
        $this->manager->flush($some);
    }
}

InMemorySomeRepository.php

<?php

namespace L3l0\InMemorySomething\Repository;

use L3l0\Something\Model\Some;
use L3l0\Something\Repository\SomeRepository;

class InMemorySomeRepository implements SomeRepository
{
    private $someCollection = [];

    public function save(Some $some)
    {
        $this->someCollection[spl_object_hash($some)] = $some;
    }
}

SomeController.php

<?php

class SomeController
{
    private $repository;

    public function __construct(SomeRepository $repository)
    {
         $this->repository = $repository;
    }

    public function doSomethingAction()
    {
        //do something
        //..

        $this->repository->save($some);
    }
}

SomeRepository.php

<?php

namespace L3l0\Something\Repository;

use L3l0\Something\Model\Some

interface SomeRepository
{
    public function save(Some $some);
}