HttpException can be differentiated via its [[statusCode]] property value which
keeps a standard HTTP status code (e.g. 404, 500). Error handlers may use this status code
to decide how to format the error page.
Throwing an HttpException like in the following example will result in the 404 page to be displayed.
php
if ($item === null) { // item does not exist
throw new \yii\web\HttpException(404, 'The requested Item could not be found.');
}