The Cache helper assists in caching entire layouts and views, saving time repetitively retrieving data. View Caching in Cake temporarily stores parsed layouts and views with the storage engine of choice. 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.
When a URL is requested, Cake 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 Cake doesn’t find a cached view, or the cache has expired for the requested URL it continues to process the request normally.
Caching is intended to be a means of temporary storage to help reduce load on the server. For example you could store the results of a time-expensive database query so that it is not required to run on every page load.
With this in mind caching is not permanent storage and should never be used to permanently store anything. And only cache things that can be regenerated when needed.
New since 1.2 are several cache engines or cache backends. These interface transparently with the cache helper, allowing you to store view caches in a multitude of media without worrying about the specifics of that media. The choice of cache engine is controlled through the app/config/core.php config file. Most options for each caching engine are listed in the core.php config file and more detailed information on each caching engine can be found in the Caching Section.
The File Engine is the default caching engine used by cake. It writes flat files to the filesystem and it has several optional parameters but works well with the defaults.
The APC engine implements the Alternative PHP Cache opcode Cacher. Like XCache, this engine caches the compiled PHP opcode.
The XCache caching engine is functionally similar to APC other than it implements the XCache opcode caching engine. It requires the entry of a user and password to work properly.
View Caching and the Cache Helper have several important configuration elements. They are detailed below.
To use the cache helper in any view or controller, you must first uncomment and set Configure::Cache.check to true in core.php of your app/config folder. If this is not set to true, then the cache will not be checked or created.
Any controllers that utilize caching functionality need to include the CacheHelper in their $helpers array.
var $helpers = array('Cache');
You also need to indicate which actions need caching, and how long each action will be cached. 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. (ie. “1 hour”, or “3 minutes”).
Using the example of an ArticlesController, that receives a lot of traffic that needs to be cached.
Cache frequently visited Articles for varying lengths of time
var $cacheAction = array( 'view/23' => 21600, 'view/48' => 36000, 'view/52' => 48000 );
Remember to use your routes in the $cacheAction if you have any.
Cache an entire action in this case a large listing of articles
var $cacheAction = array( 'archives/' => '60000' );
Cache every action in the controller using a strtotime() friendly time to indicate Controller wide caching time.
var $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:
var $cacheAction = array( 'view' => array('callbacks' => true, 'duration' => 21600), 'add' => array('callbacks' => true, 'duration' => 36000), 'index' => array('callbacks' => true, 'duration' => 48000) );
By setting callbacks => true you tell CacheHelper that you want the generated files to create the components and models for the controller. As well as, fire the component initialize, controller beforeFilter, and component startup callbacks.
callbacks => true partly defeats the purpose of caching. This is also the reason it is disabled by default.
There will be times when you don’t want an entire view cached. For example, certain parts of the page may look different whether a user is currently logged in or browsing your site as a guest.
To indicate blocks of content that are not to be cached, wrap them in <cake:nocache> </cake:nocache> like so:
<cake:nocache> <?php if ($session->check('User.name')) : ?> Welcome, <?php echo $session->read('User.name')?>. <?php else: ?> <?php echo $html->link('Login', 'users/login')?> <?php endif; ?> </cake:nocache>
It should be noted that once an action is cached, the controller method for the action will not be called - otherwise what would be the point of caching the page. Therefore, it is not possible to wrap <cake:nocache> </cake:nocache> around variables which are set from the controller as they will be null.
It is important to remember that the Cake 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.
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().