Return JSON array as resut - Provide Json Interface

You can do that using Symfony JsonResponse.

Exemple 1.
return new \Symfony\Component\HttpFoundation\JsonResponse($array);

Exemple 2.
use Symfony\Component\HttpFoundation\JsonResponse;
  public function get_result() {
    $output = array();
    $output[] = array('time' => date("Y-m-d H:i:s"));
    $output[] = array('result'=> "OK");
    return new JsonResponse($output);
  }