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##############
Caching Driver
##############
CodeIgniter features wrappers around some of the most popular forms of
fast and dynamic caching. All but file-based caching require specific
server requirements, and a Fatal Exception will be thrown if server
requirements are not met.
.. contents:: Table of Contents
*************
Example Usage
*************
The following example will load the cache driver, specify `APC <#apc>`_
as the driver to use, and fall back to file-based caching if APC is not
available in the hosting environment.
::
$this->load->driver('cache', array('adapter' => 'apc', 'backup' => 'file'));
if ( ! $foo = $this->cache->get('foo'))
{
echo 'Saving to the cache!<br />';
$foo = 'foobarbaz!';
// Save into the cache for 5 minutes
$this->cache->save('foo', $foo, 300);
}
echo $foo;
******************
Function Reference
******************
.. php:class:: CI_Cache
is_supported()
===============
.. php:method:: is_supported ( $driver )
This function is automatically called when accessing drivers via
$this->cache->get(). However, if the individual drivers are used, make
sure to call this function to ensure the driver is supported in the
hosting environment.
:param string $driver: the name of the caching driver
:returns: TRUE if supported, FALSE if not
:rtype: Boolean
::
if ($this->cache->apc->is_supported()
{
if ($data = $this->cache->apc->get('my_cache'))
{
// do things.
}
}
get()
=====
.. php:method:: get ( $id )
This function will attempt to fetch an item from the cache store. If the
item does not exist, the function will return FALSE.
:param string $id: name of cached item
:returns: The item if it exists, FALSE if it does not
:rtype: Mixed
::
$foo = $this->cache->get('my_cached_item');
save()
======
.. php:method:: save ( $id , $data [, $ttl])
This function will save an item to the cache store. If saving fails, the
function will return FALSE.
:param string $id: name of the cached item
:param mixed $data: the data to save
:param int $ttl: Time To Live, in seconds (default 60)
:returns: TRUE on success, FALSE on failure
:rtype: Boolean
::
$this->cache->save('cache_item_id', 'data_to_cache');
delete()
========
.. php:method:: delete ( $id )
This function will delete a specific item from the cache store. If item
deletion fails, the function will return FALSE.
:param string $id: name of cached item
:returns: TRUE if deleted, FALSE if the deletion fails
:rtype: Boolean
::
$this->cache->delete('cache_item_id');
clean()
=======
.. php:method:: clean ( )
This function will 'clean' the entire cache. If the deletion of the
cache files fails, the function will return FALSE.
:returns: TRUE if deleted, FALSE if the deletion fails
:rtype: Boolean
::
$this->cache->clean();
cache_info()
=============
.. php:method:: cache_info ( )
This function will return information on the entire cache.
:returns: information on the entire cache
:rtype: Mixed
::
var_dump($this->cache->cache_info());
.. note:: The information returned and the structure of the data is dependent
on which adapter is being used.
get_metadata()
===============
.. php:method:: get_metadata ( $id )
This function will return detailed information on a specific item in the
cache.
:param string $id: name of cached item
:returns: metadadta for the cached item
:rtype: Mixed
::
var_dump($this->cache->get_metadata('my_cached_item'));
.. note:: The information returned and the structure of the data is dependent
on which adapter is being used.
*******
Drivers
*******
Alternative PHP Cache (APC) Caching
===================================
All of the functions listed above can be accessed without passing a
specific adapter to the driver loader as follows::
$this->load->driver('cache');
$this->cache->apc->save('foo', 'bar', 10);
For more information on APC, please see
`http://php.net/apc <http://php.net/apc>`_
File-based Caching
==================
Unlike caching from the Output Class, the driver file-based caching
allows for pieces of view files to be cached. Use this with care, and
make sure to benchmark your application, as a point can come where disk
I/O will negate positive gains by caching.
All of the functions listed above can be accessed without passing a
specific adapter to the driver loader as follows::
$this->load->driver('cache');
$this->cache->file->save('foo', 'bar', 10);
Memcached Caching
=================
Multiple Memcached servers can be specified in the memcached.php
configuration file, located in the application/config/ directory.
All of the functions listed above can be accessed without passing a
specific adapter to the driver loader as follows::
$this->load->driver('cache');
$this->cache->memcached->save('foo', 'bar', 10);
For more information on Memcached, please see
`http://php.net/memcached <http://php.net/memcached>`_
Dummy Cache
===========
This is a caching backend that will always 'miss.' It stores no data,
but lets you keep your caching code in place in environments that don't
support your chosen cache.
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