PHP Codeigniter Integrate web service

I am integrating the CodeIgniter Rest Server library, but it does not work for me, someone could guide me correctly, I only copied the files indicated in link , but it does not work yet.

Copy the application/libraries/Format.php and application/libraries/REST_Controller.php files into the libraries folder of my project.

Also copy the application/config/rest.php file into my config folder.

Then create the Restserver driver:

defined('BASEPATH') OR exit('No direct script access allowed');
use Restserver\Libraries\REST_Controller;

class Restserver extends REST_Controller {

    public function __construct() {
        parent::__construct();

        $this->load->database();
        $this->load->helper('url');
    }
}

Then add the method to list the products:

public function products_get() {
    $this->load->model('products_model');
    $this->response($this->products_model>getproducts());
}

But when loading the page, I get error 500.