replacing the old HTML user guide with a Sphinx-managed user guide
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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.