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################
Web Page Caching
################
CodeIgniter lets you cache your pages in order to achieve maximum
performance.
Although CodeIgniter is quite fast, the amount of dynamic information
you display in your pages will correlate directly to the server
resources, memory, and processing cycles utilized, which affect your
page load speeds. By caching your pages, since they are saved in their
fully rendered state, you can achieve performance that nears that of
static web pages.
How Does Caching Work?
======================
Caching can be enabled on a per-page basis, and you can set the length
of time that a page should remain cached before being refreshed. When a
page is loaded for the first time, the cache file will be written to
your application/cache folder. On subsequent page loads the cache file
will be retrieved and sent to the requesting user's browser. If it has
expired, it will be deleted and refreshed before being sent to the
browser.
.. note: The Benchmark tag is not cached so you can still view your page
load speed when caching is enabled.
Enabling Caching
================
To enable caching, put the following tag in any of your controller
methods::
$this->output->cache($n);
Where ``$n`` is the number of **minutes** you wish the page to remain
cached between refreshes.
The above tag can go anywhere within a method. It is not affected by
the order that it appears, so place it wherever it seems most logical to
you. Once the tag is in place, your pages will begin being cached.
.. important:: Because of the way CodeIgniter stores content for output,
caching will only work if you are generating display for your
controller with a :doc:`view <./views>`.
.. note:: Before the cache files can be written you must set the file
permissions on your *application/cache/* directory such that
it is writable.
Deleting Caches
===============
If you no longer wish to cache a file you can remove the caching tag and
it will no longer be refreshed when it expires.
.. note:: Removing the tag will not delete the cache immediately. It will
have to expire normally.
If you need to manually delete the cache, you can use the ``delete_cache()``
method::
// Deletes cache for the currently requested URI
$this->output->delete_cache();
// Deletes cache for /foo/bar
$this->output->delete_cache('/foo/bar');
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