namespace App\Filters;

use CodeIgniter\HTTP\RequestInterface;
use CodeIgniter\HTTP\ResponseInterface;
use CodeIgniter\Filters\FilterInterface;

class AuthFilter implements FilterInterface
{
    public function before(RequestInterface $request, $arguments = null)
    {
        if (! session()->get('isLoggedIn')) {
            return redirect()->to('/login');
        }
    }

    public function after(RequestInterface $request, ResponseInterface $response, $arguments = null)
    {
    }
}

public $aliases = [
    'auth' => \App\Filters\AuthFilter::class,
];
public $globals = [
    'before' => ['csrf'],
];
public $filters = [
    'auth' => ['before' => ['dashboard/*']],
];

public function register()
{
    $rules = [
        'username' => 'required|min_length[3]|max_length[20]',
        'email'    => 'required|valid_email|is_unique[users.email]',
        'password' => 'required|min_length[6]',
    ];

    if (! $this->validate($rules)) {
        return view('register', [
            'validation' => $this->validator
        ]);
    }

    // Insert user
    $model = new UserModel();
    $model->save([
        'username' => $this->request->getPost('username'),
        'email'    => $this->request->getPost('email'),
        'password' => password_hash($this->request->getPost('password'), PASSWORD_BCRYPT)
    ]);

    return redirect()->to('/login');
}

// Set session
session()->set('isLoggedIn', true);

// Get session
if (session()->get('isLoggedIn')) { ... }

// Cookie
$response->setCookie('remember', 'yes', 3600);

$file = $this->request->getFile('avatar');
if ($file->isValid() && !$file->hasMoved()) {
    $file->move(WRITEPATH.'uploads');
}

$image = \Config\Services::image()
    ->withFile(WRITEPATH.'uploads/'.$file->getName())
    ->resize(300, 300, true)
    ->save(WRITEPATH.'uploads/thumb_'.$file->getName());

$model = new UserModel();
$data['users'] = $model->paginate(10);
$data['pager'] = $model->pager;

return view('users/list', $data);

<?= $pager->links() ?>

public $protocol = 'smtp';
public $SMTPHost = 'smtp.gmail.com';
public $SMTPUser = '[email protected]';
public $SMTPPass = 'app-password';
public $SMTPPort = 587;
public $mailType = 'html';

$email = \Config\Services::email();
$email->setTo('[email protected]');
$email->setSubject('Welcome!');
$email->setMessage('Cảm ơn bạn đã đăng ký.');
$email->send();

log_message('error', 'Có lỗi: {data}', ['data' => $info]);