//...
use Symfony\Component\HttpFoundation\Response;
 
class MyController extends AbstractController
{
    //...
 
    /**
     * @Route("/test", name="test")
     */
    public function test(...): Response
    {
        //...
        $tableau = [ ... ];
        $status = 200;
        return $this->json($tableau, $status);
    }
 
}

//...
use Symfony\Component\HttpFoundation\HeaderUtils;
use Symfony\Component\HttpFoundation\Response;
 
class MyController extends AbstractController
{
    //...
 
    /**
     * @Route("/export", name="export")
     */
    public function export(...): Response
    {
        //...
        $tableau = [ ... ];
        $status = 200;
        return $this->json($tableau, $status, [
            'Content-Disposition' => HeaderUtils::makeDisposition(
                HeaderUtils::DISPOSITION_ATTACHMENT,
                'export-' . $now->format('Ymd-Hms') . '.json'
            )
        ]);
    }
 
}