<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Caching Driver : CodeIgniter User Guide</title>

<style type='text/css' media='all'>@import url('../userguide.css');</style>
<link rel='stylesheet' type='text/css' media='all' href='../userguide.css' />

<script type="text/javascript" src="../nav/nav.js"></script>
<script type="text/javascript" src="../nav/prototype.lite.js"></script>
<script type="text/javascript" src="../nav/moo.fx.js"></script>
<script type="text/javascript" src="../nav/user_guide_menu.js"></script>

<meta http-equiv='expires' content='-1' />
<meta http-equiv= 'pragma' content='no-cache' />
<meta name='robots' content='all' />
<meta name='author' content='ExpressionEngine Dev Team' />
<meta name='description' content='CodeIgniter User Guide' />

</head>
<body>

<!-- START NAVIGATION -->
<div id="nav"><div id="nav_inner"><script type="text/javascript">create_menu('../');</script></div></div>
<div id="nav2"><a name="top"></a><a href="javascript:void(0);" onclick="myHeight.toggle();"><img src="../images/nav_toggle_darker.jpg" width="154" height="43" border="0" title="Toggle Table of Contents" alt="Toggle Table of Contents" /></a></div>
<div id="masthead">
<table cellpadding="0" cellspacing="0" border="0" style="width:100%">
<tr>
<td><h1>CodeIgniter User Guide Version 2.0.0</h1></td>
<td id="breadcrumb_right"><a href="../toc.html">Table of Contents Page</a></td>
</tr>
</table>
</div>
<!-- END NAVIGATION -->


<!-- START BREADCRUMB -->
<table cellpadding="0" cellspacing="0" border="0" style="width:100%">
<tr>
<td id="breadcrumb">
<a href="http://codeigniter.com/">CodeIgniter Home</a> &nbsp;&#8250;&nbsp;
<a href="../index.html">User Guide Home</a> &nbsp;&#8250;&nbsp;
<a href="../general/drivers.html">Drivers</a> &nbsp;&#8250;&nbsp;
Caching Driver
</td>
<td id="searchbox"><form method="get" action="http://www.google.com/search"><input type="hidden" name="as_sitesearch" id="as_sitesearch" value="codeigniter.com/user_guide/" />Search User Guide&nbsp; <input type="text" class="input" style="width:200px;" name="q" id="q" size="31" maxlength="255" value="" />&nbsp;<input type="submit" class="submit" name="sa" value="Go" /></form></td>
</tr>
</table>
<!-- END BREADCRUMB -->

<br clear="all" />


<!-- START CONTENT -->
<div id="content">

<h1>Caching Driver</h1>

<p>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.</p>

<h2>Table of Contents</h2>
<ul>
	<li><a href="#example_usage" title="Example Usage">Example Usage</a></li>
	<li><a href="#function_reference" title="Function Reference">Function Reference</a></li>
</ul>

<h3>Available Drivers</h3>
<ul>
	<li><a href="#apc" title="APC Cache">Alternative PHP Cache (APC) Caching</a></li>
	<li><a href="#file" title="File Caching">File-based Caching</a></li>
	<li><a href="#memcached" title="Memcached">Memcached Caching</a></li>
	<li><a href="#dummy" title="Dummy Caching">Dummy Cache</a></li>
</ul>

<h2 id="example_usage">Example Usage</h2>

<p>The following example will load the cache driver, specify <a href="#apc" title="APC">APC</a> as the driver to use, and fall back to file-based caching if APC is not available in the hosting environment.</p>

<code>
$this->load->driver('cache', array('adapter' => 'apc', 'backup' => 'file'));<br />
<br />
if ( ! $foo = $this->cache->get('foo'))<br />
{<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;echo 'Saving to the cache!&lt;br />';<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$foo = 'foobarbaz!';<br />
<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// Save into the cache for 5 minutes<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$this->cache->save('foo', $foo, 300);<br />
}<br />
<br />
echo $foo;
</code>

<h1 id="function_reference">Function Reference</h1>

<h2>is_supported(<var>driver</var>['string'])</h2>

<p>This function is automatically called when accessing drivers via <samp>$this->cache->get()</samp>.  However, if the individual drivers are used, make sure to call this function to ensure the driver is supported in the hosting environment.</p>

<code>
if ($this->cache->apc->is_supported())<br />
{<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if ($data = $this->cache->apc->get('my_cache'))<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// do things.<br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<br />
}
</code>

<h2>get(<var>id</var>['string'])</h2>

<p>This function will attempt to fetch an item from the cache store.  If the item does not exist, the function will return <samp>FALSE</samp>.</p>
<code>$foo = $this->cache->get('my_cached_item');</code>

<h2>save(<var>id</var>['string'], <var>data</var>['mixed'], <var>ttl</var>['int'])</h2>

<p>This function will save an item to the cache store.  If saving fails, the function will return <samp>FALSE</samp>.</p>
<p>The optional third parameter (Time To Live) defaults to 60 seconds.</p>
<code>$this->cache->save('cache_item_id', 'data_to_cache');</code>

<h2>delete(<var>id</var>['string'])</h2>

<p>This function will delete a specific item from the cache store.  If item deletion fails, the function will return <samp>FALSE</samp>.</p>
<code>$this->cache->delete('cache_item_id');</code>

<h2>clean()</h2>

<p>This function will 'clean' the entire cache.  If the deletion of the cache files fails, the function will return <samp>FALSE</samp>.</p>

<code>$this->cache->clean();</code>

<h2>cache_info()</h2>

<p>This function will return information on the entire cache.</p>

<code>var_dump($this->cache->cache_info());</code>

<h2>get_metadata(<var>id</var>['string'])</h2>

<p>This function will return detailed information on a specific item in the cache.</p>

<code>var_dump($this->cache->get_metadata('my_cached_item'));</code>

<h1>Drivers</h1>

<h2 id="apc">Alternative PHP Cache (APC) Caching</h2>

<p>All of the functions listed above can be accessed without passing a specific adapter to the driver loader as follows:</p>
<code>$this->load->driver('cache');<br />
	$this->cache->apc->save('foo', 'bar', 10);</code>
<p>For more information on APC, please see <a href="http://php.net/apc">http://php.net/apc</a></p>

<h2 id="file">File-based Caching</h2>

<p>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.</p>

<p>All of the functions listed above can be accessed without passing a specific adapter to the driver loader as follows:</p>
<code>$this->load->driver('cache');<br />
	$this->cache->file->save('foo', 'bar', 10);</code>

<h2 id="memcached">Memcached Caching</h2>

<p>Multiple Memcached servers can be specified in the memcached.php configuration file, located in the <samp>application/config/</samp> directory.

<p>All of the functions listed above can be accessed without passing a specific adapter to the driver loader as follows:</p>
<code>$this->load->driver('cache');<br />
	$this->cache->memcached->save('foo', 'bar', 10);</code>

<p>For more information on Memcached, please see <a href="http://php.net/memcached">http://php.net/memcached</a></p>

<h2 id="dummy">Dummy Cache</h2>

<p>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.</p>

</div>
<!-- END CONTENT -->


<div id="footer">
<p>
Previous Topic:&nbsp;&nbsp;<a href="errors.html">Error Handling</a>
&nbsp;&nbsp;&nbsp;&middot;&nbsp;&nbsp;
<a href="#top">Top of Page</a>&nbsp;&nbsp;&nbsp;&middot;&nbsp;&nbsp;
<a href="../index.html">User Guide Home</a>&nbsp;&nbsp;&nbsp;&middot;&nbsp;&nbsp;
Next Topic:&nbsp;&nbsp;<a href="profiling.html">Profiling Your Application</a>
</p>
<p><a href="http://codeigniter.com">CodeIgniter</a> &nbsp;&middot;&nbsp; Copyright &#169; 2006 - 2011 &nbsp;&middot;&nbsp; <a href="http://ellislab.com/">EllisLab, Inc.</a></p>
</div>

</body>
</html>