try to use interface in codeigniter 3.0 return error Fatal error: Interface 'crudmodelinterface' not found

Question

I want to use an interface inside the Codeigniter framework.

I'm using a fresh built Codeigniter 3.0 project, and by following a tutorial I created the following:

MY_Loader in application/core

<?php
class MY_Loader extends CI_Loader
{
  /**
   * List of paths to load interfaces from
   *
   * @var array
   * @access protected
   */
  protected $_ci_interface_paths    = array();
  function __construct()
  {
    parent::__construct();
    //we do all the standard Loader construction, then also set up the acceptable places to look for interfaces
    $this->_ci_interface_paths = array(APPPATH, BASEPATH);
  }
 
  public function initialize()
  {
    parent::initialize();
    // After the parent is initialized, we load the autoload config
    if (defined('ENVIRONMENT') AND file_exists(APPPATH.'config/'.ENVIRONMENT.'/autoload.php'))
    {
      include(APPPATH.'config/'.ENVIRONMENT.'/autoload.php');
    }
    else
    {
      include(APPPATH.'config/autoload.php');
    }
    // and if $autoload['interface'] is in the config, load each one
    if (isset($autoload['interface']))
    {
      foreach($autoload['interface'] as $interface)
        $this->iface($interface);
    }
  }
 
  /**
   * Load an interface from /application/interfaces
   *
   * @param $interface string The interface name
   * @return CI_Loader for chaining */
  public function iface($interface = '')
  {
    $class = str_replace('.php', '', trim($interface, '/'));
 
    // Was the path included with the interface name?
    // We look for a slash to determine this
    $subdir = '';
    if (($last_slash = strrpos($class, '/')) !== FALSE)
    {
      // Extract the path
      $subdir = substr($class, 0, $last_slash + 1);
 
      // Get the filename from the path
      $class = substr($class, $last_slash + 1);
    }
    // Look for the interface path and include it
    $is_duplicate = FALSE;
    foreach ($this->_ci_interface_paths as $path)
    {
      $filepath = $path.'interfaces/'.$subdir.$class.'.php';
 
      // Does the file exist?  No? Try the remaining paths
      if ( ! file_exists($filepath))
      {
        continue;
      }
 
      include_once($filepath);
      $this->_ci_loaded_files[] = $filepath;
      return $this;
    }
  }
}
/* End of file MY_Loader.php */
/* Location: ./application/core/MY_Loader.php */

Create new folder interfaces in application and under application/interfaces create file crudmodelinterface.php

<?php
interface crudmodelinterface {
    public function create();
    public function load();
    public function update();
    public function delete();
}

And in autoload.php in application/config I added this code:

$autoload['interface'] = array('crudmodelinterface');

In file controller Welcome.php I implemented crudmodelinterface:

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Welcome extends CI_Controller implements crudmodelinterface{

    /**
     * Index Page for this controller.
     *
     * Maps to the following URL
     *      http://example.com/index.php/welcome
     *  - or -
     *      http://example.com/index.php/welcome/index
     *  - or -
     * Since this controller is set as the default controller in
     * config/routes.php, it's displayed at http://example.com/
     *
     * So any other public methods not prefixed with an underscore will
     * map to /index.php/welcome/<method_name>
     * @see http://codeigniter.com/user_guide/general/urls.html
     */
    public function index()
    {
        $this->load->view('welcome_message');
    }
    public function create(){}
    public function load(){}
    public function update(){}
    public function delete(){}

}

BUT when I access the controller it return this error:

Fatal error: Interface 'crudmodelinterface' not found in C:\xampp\htdocs\test_interface\application\controllers\Welcome.php on line 4

How to fix this error?