$this->view->disable();
$response->setContentType('application/json', 'UTF-8');
$this->response->setJsonContent($result);
$this->response->send();
Alternatively:
$this->view->disable();
header('Content-type:application/json');
echo json_encode($result,JSON_NUMERIC_CHECK);
The first code is the correct way especially if you are using phpdebugbar which will try and echo out its javascript if you use the second non-phalcon version.