Symfony 2使用AJAX获取表单错误

$errors = array();

if ($form instanceof Form) {

    foreach ($form->getErrors(true, true) as $error) {
         $errors[] = $error->getMessage();
    }
}

I'm using AJAX request with my registration form. The JSON response now is like: ["error1", "error2", "error3"] . Code above works for me but I would like to get fields names aswell. I've tried few solutions but any of them works for me.