frontend\controllers\CategoryController::actionIndex PHP Method

    public function actionIndex($slug = 'index')
    {
        if (empty($slug) || $slug == 'index') {
            throw new NotFoundHttpException('Page not found.');
        } else {
            $category = Category::find()->where(['slug' => $slug]);
            $categoryCount = clone $category;
            if (!$categoryCount->count()) {
                throw new NotFoundHttpException('Page not found.');
            }
        }
        $query = Post::find()->joinWith('category')->where(['status' => Post::STATUS_PUBLISHED, Category::tableName() . '.slug' => $slug])->orderBy('published_at DESC');
        $countQuery = clone $query;
        $pagination = new Pagination(['totalCount' => $countQuery->count(), 'defaultPageSize' => Yii::$app->settings->get('reading.page_size', 10)]);
        $posts = $query->offset($pagination->offset)->limit($pagination->limit)->all();
        return $this->render('index', ['posts' => $posts, 'category' => $category->one(), 'pagination' => $pagination]);
    }