Postman的GET请求没有显示JSON输出

Question

I'm working with a PHP REST API, I made this function:

 function getNotifications($request) {
     require_once 'db.php';
     $emp = json_decode($request->getBody());
     $id = $request->getAttribute("id");
     $sql = "select * FROM notifications WHERE userid= :userid";

     try {
         $db = getConnection();
         $stmt = $db->prepare($sql);
         $stmt->bindParam("userid", $id);
         $stmt->execute();
         $wines = $stmt->fetch(PDO::FETCH_OBJ);
         $db = null;

         return json_encode($wines);
     } catch(PDOException $e) {
         echo '{"error":{"text":'. $e->getMessage() .'}}';
     }
}

When I try to echo the wines variable, echo wines->message;, it's working, so the problem isn't from the query.
The problem is that when I try to make a call to the API without echo, nothing shows off, not even a message saying that I have no result.