DTO example

AbstractRequest.php

<?php

namespace SomeApp\Application\DTO;

use Symfony\Component\OptionsResolver\OptionsResolver;

abstract class AbstractRequest
{

    public function __construct(array $data)
    {
        $options = new OptionsResolver();
        $this->configureOptions($options);

        $this->map($options);
    }

    abstract protected function configureOptions(OptionsResolver $options);

    protected function map(OptionsResolver $options)
    {
        // just plain mapping, all other things 
        // like snake case to camel case convertion or keys aliases resolving
        // should be done in controller
        // values normalization could be done via option resolver's normalizers
        $options->resolve($data);
        foreach ($options->getDefinedOptions() as $prop) {
            $this->$prop = $options[$prop];
        }
    }
}

DoSomethingRequest.php

<?php

namespace SomeApp\Application\DTO\Something;

use Symfony\Component\OptionsResolver\OptionsResolver;
use SomeApp\Infrastructure\Security\UserSession;

class DoSomethingRequest extends AbstractRequest
{
    protected $userSession;
    
    protected $foo;
    
    protected $fooBar;
  
    /**
     * @param UserSession $userSession - id of user
     * @param array $data - array of options to be resolved
     */
    public function __construct(UserSession $userSession, array $data)
    {
        // this is only for example,
        // I usually have UserSession object wich implements UserInterface
        // UserSession isn't doctrine entity, it just data container which hydrates from JWT token
        // It contains user Id, some other information (isAdmin flag for example) and so on.
        $this->userSession = $userSession; 
        
        parent::__contruct($data);
    }

    protected function configureOptions(OptionsResolver $options)
    {
      $options
        ->setRequired(['foo', 'bar'])
        ->setAllowedTypes([
          'foo' => 'string',
          'fooBar' => ['int', 'string']
        ])
      ;
    }
    
    public function getUserID()
    {
        return $this->userSession->getUserID();
    }
    
    public function getFoo()
    {
        return $this->foo;
    }

    public function getFooBar()
    {
        return $this->fooBar;
    }
}

SomethingController.php

<?php

class SomethingController extends Controller
{
  
    public function createSomething(Request $request) {
      // handled via symfony/serializer in middleware
      // or you can map it with jms serializer or just by yourself here in controller
      $requestData = $request->request->all();
      // create request DTO
      $requestDTO = new DoSomethingRequest($this->getUser(), $requestData);
      // pass it to application layer, which will return response dto
      $responseDTO = $this->get('something_maker')->doStuff($requestDTO);
      
      return $responseDTO; // middleware will serialize it, or we can use JsonResponse and map data to array...
    }
    
}

I've did not check the whole code, but you can improve your abstract request class.

First, what kind of request is it? A http request? I know, this is for demonstration purpose, but in that case the AbstractSomerRequest could be more luckily.

Based on this: (http://misko.hevery.com/code-reviewers-guide/flaw-constructor-does-real-work/) the constructor of this class should be:

public function __construct(array $data, OptionResolver $options)