Rest API Codeigniter. CORS PROBLEM [SOLVED]

Ok, I tried to host the frontend (reactjs) on a server with an accessible domain, then I tried one request and it doesn't work.
I've always this error:

UPDATE: SOLVED!

So, I was using IIS, so I added to my web.config:

Code:

<httpProtocol>
 <customHeaders>
   <add name="Access-Control-Allow-Origin" value="*" />
   <add name="Access-Control-Allow-Headers" value="Content-Type" />
   <add name="Access-Control-Allow-Methods" value="GET, POST, PUT, DELETE, OPTIONS" />
 </customHeaders>
</httpProtocol>

then I changed my controller to that

PHP Code:

<?php
/**
 * Created by PhpStorm.
 * User: Edoardo
 * Date: 15/04/2018
 * Time: 18:26
 */

require APPPATH . 'libraries/REST_Controller.php';

class Login extends REST_Controller
{

    public function __construct($config = 'rest')
    {
        parent::__construct($config);


    }

    public function index_post(){
        echo json_encode(array("hey" => "hey!"));
    }

    public function index_options() {
        return $this->response(NULL, REST_Controller::HTTP_OK);
    }

} 


and now it works!