Page Caching

Page caching refers to caching the content of a whole page. Page caching can occur at different places. For example, by choosing an appropriate page header, the client browser may cache the page being viewed for a limited time. The Web application itself can also store the page content in cache. In this subsection, we focus on this latter approach.

Page caching can be considered as a special case of fragment caching. Because the content of a page is often generated by applying a layout to a view, it will not work if we simply call beginCache() and endCache() in the layout. The reason is because the layout is applied within the CController::render() method AFTER the content view is evaluated.

To cache a whole page, we should skip the execution of the action generating the page content. We can use COutputCache as an action filter to accomplish this task. The following code shows how we configure the cache filter:

public function filters()
{
    return array(
        array(
            'COutputCache',
            'duration'=>100,
            'varyByParam'=>array('id'),
        ),
    );
}

The above filter configuration would make the filter to be applied to all actions in the controller. We may limit it to one or a few actions only by using the plus operator. More details can be found in filter.

Tip: We can use COutputCache as a filter because it extends from CFilterWidget, which means it is both a widget and a filter. In fact, the way a widget works is very similar to a filter: a widget (filter) begins before any enclosed content (action) is evaluated, and the widget (filter) ends after the enclosed content (action) is evaluated.