CaracoleBundle/Controller/Merchant/SwitchMerchantController.php

<?php

namespace Lc\CaracoleBundle\Controller\Merchant;

use Lc\CaracoleBundle\Form\Merchant\SwitchMerchantFormType;
use Lc\SovBundle\Doctrine\EntityManager;
use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\Security\Core\Security;

class SwitchMerchantController extends AbstractController
{

    public function switchMerchant(Request $request, Security $security, EntityManager $em)
    {
        $user = $security->getUser() ;

        if($user) {
            $form = $this->createForm(SwitchMerchantFormType::class);
            $form->handleRequest($request);

            if ($form->isSubmitted() && $form->isValid()) {
                $merchant = $form->get('merchants')->getData();
                $user->setFavoriteMerchant($merchant) ;
                $em->update($user) ;
                $em->flush() ;

                return $this->redirectToRoute('admin_dashboard') ;
            }
        }
        else {

        }
    }
}