How to competently close the site by option?

Question

Yii

If Yii::$app->params['is_offline'] == 1 I need to close the site, but access to the admin panel should remain. The admin panel is made simply by a module, on the same domain. Tell me how best to do this?
In which file should the check be done, not in the index.php?
and how to make a check so that access to the admin panel remains

Answer 1

While waiting for an answer, I myself came up with such a solution, please check it out.
in config

'bootstrap' => [
        'app\components\MainComponent',
    ],

and MainComponent itself

class MainComponent extends Component
{
    public $roles = ['root', 'admin']; // разрешенные роли

    public function init()
    {
        if (Yii::$app->params['is_offline'] == 1) {
            $enable_role = in_array(Yii::$app->user->identity->role, $this->roles);

            $ips = explode(',', Yii::$app->params['allow_ip']);
            $ips = array_map("trim", $ips);
            $enable_ip = in_array($this->getIp(), $ips); //check "allowed IP"

            if(!$enable_role AND !$enable_ip) {
                die(Yii::$app->params['closeText']);
            }
        }
    }

Answer 2

not in index.php?

Why not?
Just connect different configs in index php depending on the need. In yii2, there is initially a similar feature for dev and prod. Add the close option, while connecting the admin module in the config and do not connect others or anything else.