Doctrine2toXML.php

<?php

// Propel way
$books = BookQuery::create()->find();
$xmlBooks = $books->toXml();

// Doctrine way
// $this is a symfony controller having access to the DIC
$em = $this->get('doctrine.orm.entity_manager');
$books = $em->createQuery('select b from \Acme\DemoBundle\Entity\Book b')->getResult();
$serializer = new \Symfony\Component\Serializer\Serializer();
$serializer->addNormalizer(new \Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer());
$serializer->setEncoder('xml', new \Symfony\Component\Serializer\Encoder\XmlEncoder());
$xmlBooks = $serializer->serialize($books, 'xml');

If you're going to use DI you need a configuration layer, which the DIC provides. In this gist you're misusing the DIC by injecting it instead of your actual dependencies. With proper DI this becomes...

$xmlBooks = $serializer->serialize($bookRepo->findAll(), 'xml');

If I understand you correctly, I have to define some configuration for 3 service classes in a separate file just to do something like '->toXml()'? It's probably better in the controller class, but it's still very verbose overall.

Would you have an example of the DIC configuration it requires?

Yes, if you're following DI, that's how I would do it.

my_controller:
    class: MyController
    arguments:
        - @book_repo
        - @serializer

But the serializer needs to be defined as well in the DIC, doesn't it?

Yes, I'm not familiar with the Serializer component, but the configuration would look similar.