app\controllers\SiteController::actionError PHP Method

    public function actionError()
    {
        if (($exception = Yii::$app->getErrorHandler()->exception) === null) {
            return '';
        }
        if ($exception instanceof HttpException) {
            $code = $exception->statusCode;
        } else {
            $code = $exception->getCode();
        }
        if ($exception instanceof Exception) {
            $name = $exception->getName();
        } else {
            $name = Yii::t('yii', 'Error');
        }
        if ($code) {
            $name .= " (#{$code})";
        }
        if ($exception instanceof \Exception) {
            $message = $exception->getMessage();
        } else {
            $message = Yii::t('yii', 'An internal server error occurred.');
        }
        if (Yii::$app->getRequest()->getIsAjax()) {
            static::renderJson([], $code ?: -1, $message);
        } else {
            return $this->render('error', ['name' => $name, 'message' => $message, 'exception' => $exception]);
        }
    }