qii/demo/private/middleware/auth.php

<?php
namespace middleware;

use Closure;
use Qii\Base\Middleware\Request as Middleware;
use \Qii\Base\Request;

class auth implements Middleware
{
    public function __construct()
    {
    }
    public function handle(Request $request, Closure $next) {
        if (!$_SESSION['admin']) {
            return "This need login <br />";
        }
        return $next($request);
    }
}