yii2/docs/guide/authorization.md

Authorization

Authorization is the process of verifying that user has enough permissions to do something. Yii provides several methods of controlling it.

Access control basics

Basic access control is very simple to implement using yii\filters\AccessControl:

class SiteController extends Controller
{
    public function behaviors()
    {
        return [
            'access' => [
                'class' => \yii\filters\AccessControl::className(),
                'only' => ['login', 'logout', 'signup'],
                'rules' => [
                    [
                        'actions' => ['login', 'signup'],
                        'allow' => true,
                        'roles' => ['?'],
                    ],
                    [
                        'actions' => ['logout'],
                        'allow' => true,
                        'roles' => ['@'],
                    ],
                ],
            ],
        ];
    }
    // ...

In the code above we're attaching access control behavior to a controller. Since there's only option specified, it will be applied to 'login', 'logout' and 'signup' actions only. A set of rules that are basically options for yii\filters\AccessRule reads as follows:

• Allow all guest (not yet authenticated) users to access 'login' and 'signup' actions.
• Allow authenticated users to access 'logout' action.

Rules are checked one by one from top to bottom. If rule matches, action takes place immediately. If not, next rule is checked. If no rules matched access is denied.

yii\filters\AccessRule is quite flexible and allows additionally to what was demonstrated checking IPs and request method (i.e. POST, GET). If it's not enough you can specify your own check via anonymous function:

class SiteController extends Controller
{
    public function behaviors()
    {
        return [
            'access' => [
                'class' => \yii\filters\AccessControl::className(),
                'only' => ['special-callback'],
                'rules' => [
                    [
                        'actions' => ['special-callback'],
                        'allow' => true,
                        'matchCallback' => function ($rule, $action) {
                            return date('d-m') === '31-10';
                        }
                    ],

And the action:

    // ...
    // Match callback called! This page can be accessed only each October 31st
    public function actionSpecialCallback()
    {
        return $this->render('happy-halloween');
    }

Sometimes you want a custom action to be taken when access is denied. In this case you can specify denyCallback.

Role based access control (RBAC)

Role based access control is very flexible approach to controlling access that is a perfect match for complex systems where permissions are customizable.