Makes data in `$request->request` accessible for other ParamConverters like `DoctrineParamConverter`. Just use the `from` option in your annotations, like in the example.

ExampleController.php

use Sensio\Bundle\FrameworkExtraBundle\Configuration\ParamConverter;

class ExampleController
{
    /**
     * @ParamConverter("user", {"from" = "id"})
     */
    public function exampleAction(User $user)
    {
        // …
    }
}

PostParamConverter.php

<?php

use Sensio\Bundle\FrameworkExtraBundle\Configuration\ConfigurationInterface;
use Sensio\Bundle\FrameworkExtraBundle\Configuration as Annotation;
use Sensio\Bundle\FrameworkExtraBundle\Request\ParamConverter\ParamConverterInterface;
use Symfony\Component\HttpFoundation\Request;

class PostParamConverter implements ParamConverterInterface
{
    public function apply(Request $request, ConfigurationInterface $configuration)
    {
        if (!$this->supports($configuration) || !$this->supportsRequest($request)) {
            return;
        }

        $options = $this->getOptions($configuration);

        $name = $configuration->getName();
        if (null === $request->attributes->get($name, false)) {
            $configuration->setIsOptional(true);
        }

        $value = $request->request->get($options['from'], null);
        if ($value === null && !$configuration->isOptional()) {
            throw new \LogicException('Unable to guess how to get a Post instance from the request information.');
        }

        $name = isset($options['id']) ? $options['id'] : $configuration->getName();
        $request->attributes->set($name, $value);
    }

    public function supports(ConfigurationInterface $configuration)
    {
        return $configuration instanceof Annotation\ParamConverter && $this->supportOptions($configuration);
    }

    protected function supportOptions(Annotation\ParamConverter $configuration)
    {
        $options = $configuration->getOptions();

        return isset($options['from']);
    }

    protected function supportsRequest(Request $request)
    {
        return 'GET' !== $request->getMethod();
    }

    protected function getOptions(Annotation\ParamConverter $configuration)
    {
        return $configuration->getOptions();
    }
}

services.yml

service.param_converter.post:
    class: PostParamConverter
    tags:
        - { name: request.param_converter, priority: 10 } # Higher priority than DoctrineParamConverter