LcShopBundle/ShopBundle/Controller/Admin/MerchantController.php

<?php

namespace Lc\ShopBundle\Controller\Admin;

use Lc\ShopBundle\Context\MerchantInterface;
use Symfony\Component\HttpFoundation\RedirectResponse;
use Symfony\Component\HttpFoundation\Request;

class MerchantController extends AdminController
{

        public function switchMerchantAction(Request $request): RedirectResponse
        {
                $em = $this->getDoctrine()->getManager();
                $idMerchant = $request->request->get('id_merchant') ;
                $merchant = $this->getDoctrine()
                        ->getRepository(MerchantInterface::class)
                        ->find($idMerchant);

                if($merchant) {
                        $user = $this->security->getUser() ;
                        $user->setMerchant($merchant) ;
                        $em->persist($user);
                        $em->flush() ;
                }

                return $this->redirect('admin/dashboard') ;
        }

}