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CacheHelper

class CacheHelper(View $view, array $settings = array())

The Cache helper assists in caching entire layouts and views, saving time repetitively retrieving data. View Caching in CakePHP temporarily stores parsed layouts and views as simple PHP + HTML files. It should be noted that the Cache helper works quite differently than other helpers. It does not have methods that are directly called. Instead, a view is marked with cache tags indicating which blocks of content should not be cached. The CacheHelper then uses helper callbacks to process the file and output to generate the cache file.

When a URL is requested, CakePHP checks to see if that request string has already been cached. If it has, the rest of the URL dispatching process is skipped. Any nocache blocks are processed normally and the view is served. This creates a big savings in processing time for each request to a cached URL as minimal code is executed. If CakePHP doesn’t find a cached view, or the cache has expired for the requested URL it continues to process the request normally.

Using the Helper

There are two steps you have to take before you can use the CacheHelper. First in your APP/Config/core.php uncomment the Configure write call for Cache.check. This will tell CakePHP to check for, and generate view cache files when handling requests.

Once you’ve uncommented the Cache.check line you will need to add the helper to your controller’s $helpers array:

class PostsController extends AppController {
    public $helpers = array('Cache');
}

You will also need to add the CacheDispatcher to your dispatcher filters in your bootstrap:

Configure::write('Dispatcher.filters', array(
    'CacheDispatcher'
));

New in version 2.3: If you have a setup with multiple domains or languages you can use Configure::write(‘Cache.viewPrefix’, ‘YOURPREFIX’); to store the view cache files prefixed.

Additional configuration options

CacheHelper has a few additional configuration options you can use to tune and tweak its behavior. This is done through the $cacheAction variable in your controllers. $cacheAction should be set to an array which contains the actions you want cached, and the duration in seconds you want those views cached. The time value can be expressed in a strtotime() format (e.g. “1 hour”, or “3 minutes”).

Using the example of an ArticlesController, that receives a lot of traffic that needs to be cached:

public $cacheAction = array(
    'view' => 36000,
    'index' => 48000
);

This will cache the view action 10 hours, and the index action 13 hours. By making $cacheAction a strtotime() friendly value you can cache every action in the controller:

public $cacheAction = "1 hour";

You can also enable controller/component callbacks for cached views created with CacheHelper. To do so you must use the array format for $cacheAction and create an array like the following:

public $cacheAction = array(
    'view' => array('callbacks' => true, 'duration' => 21600),
    'add' => array('callbacks' => true, 'duration' => 36000),
    'index' => array('callbacks' => true, 'duration' => 48000)
);

By setting callbacks => true you tell CacheHelper that you want the generated files to create the components and models for the controller. Additionally, fire the component initialize, controller beforeFilter, and component startup callbacks.

Note

Setting callbacks => true partly defeats the purpose of caching. This is also the reason it is disabled by default.

Marking Non-Cached Content in Views

There will be times when you don’t want an entire view cached. For example, certain parts of the page may look different whether a user is currently logged in or browsing your site as a guest.

To indicate blocks of content that are not to be cached, wrap them in <!--nocache--> <!--/nocache--> like so:

<!--nocache-->
<?php if ($this->Session->check('User.name')): ?>
    Welcome, <?php echo h($this->Session->read('User.name')); ?>.
<?php else: ?>
    <?php echo $this->Html->link('Login', 'users/login'); ?>
<?php endif; ?>
<!--/nocache-->

Note

You cannot use nocache tags in elements. Since there are no callbacks around elements, they cannot be cached.

It should be noted that once an action is cached, the controller method for the action will not be called. When a cache file is created, the request object, and view variables are serialized with PHP’s serialize().

Warning

If you have view variables that contain un-serializable content such as SimpleXML objects, resource handles, or closures you might not be able to use view caching.

Clearing the Cache

It is important to remember that CakePHP will clear a cached view if a model used in the cached view is modified. For example, if a cached view uses data from the Post model, and there has been an INSERT, UPDATE, or DELETE query made to a Post, the cache for that view is cleared, and new content is generated on the next request.

Note

This automatic cache clearing requires the controller/model name to be part of the URL. If you’ve used routing to change your URLs this feature will not work.

If you need to manually clear the cache, you can do so by calling Cache::clear(). This will clear all cached data, excluding cached view files. If you need to clear the cached view files, use clearCache().