set_cookie & redirect() didn't work

Hello,

Here is my User controller code. I don't know why the function "set_cookie" didn't work. It redirected to the home page, but it didn't set the cookie in the browser. Please help.

PHP Code:

<?php namespace App\Controllers;

use CodeIgniter\Controller;

class User extends BaseController
{
  public function index()
  {
    return view('welcome_message');
  }

  public function login()
    {
    $data = [];
    if($this->request->getMethod() == 'post')
    {
      if(!$this->validate([
        'username' => ['label' => 'Username', 'rules' => 'required'],
        'password' => ['label' => 'Password', 'rules' => 'required'],
      ]))
      {
        $data['errors'] = $this->validator->getErrors();
      }
      else
      {
        set_cookie('login', md5($this->request->getVar('password')), time() + 86400);
        return redirect()->to('/');
      }
    }
        return view('login', $data);
    }

  public function logout()
    {
    delete_cookie('login');
        return redirect()->to('/');
    }
  
}