frontend/controllers/SiteController.php

<?php
    namespace frontend\controllers;
    
    use yii\web\Controller;
    use yii\filters\VerbFilter;
    use yii\filters\AccessControl;
    
    /**
     * Site controller
     */
    class SiteController extends Controller
    {
        
        /**
         * @inheritdoc
         */
        public function behaviors()
        {
            return [
                'access' => [
                    'class' => AccessControl::className(),
                    'only'  => [
                        'logout',
                        'signup',
                    ],
                    'rules' => [
                        [
                            'actions' => [ 'signup' ],
                            'allow'   => true,
                            'roles'   => [ '?' ],
                        ],
                        [
                            'actions' => [ 'logout' ],
                            'allow'   => true,
                            'roles'   => [ '@' ],
                        ],
                    ],
                ],
                'verbs'  => [
                    'class'   => VerbFilter::className(),
                    'actions' => [
                        'logout' => [ 'post' ],
                    ],
                ],
            ];
        }
        
        /**
         * @inheritdoc
         */
        public function actions()
        {
            return [
                'error'   => [
                    'class' => 'yii\web\ErrorAction',
                ],
                'captcha' => [
                    'class'           => 'yii\captcha\CaptchaAction',
                    'fixedVerifyCode' => YII_ENV_TEST ? 'testme' : null,
                ],
            ];
        }
        
        /**
         * Displays homepage.
         *
         * @return mixed
         */
        public function actionIndex()
        {
            return $this->render('index');
        }
    }