<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html><head><title>CodeIgniter User Guide : Web Page Caching</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="Content-Type" content="text/html; charset=utf-8" /><meta http-equiv='expires' content='-1' /><meta http-equiv= 'pragma' content='no-cache' /><meta name='robots' content='all' /><meta name='author' content='Rick Ellis' /><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.jpg" width="153" height="44" 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 1.5.4</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://www.codeigniter.com/">CodeIgniter Home</a> &nbsp;&#8250;&nbsp;<a href="../index.html">User Guide Home</a> &nbsp;&#8250;&nbsp;Page Caching</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>Web Page Caching</h1><p>CodeIgniter lets you cache your pages in order to achieve maximum performance.</p><p>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.</p><h2>How Does Caching Work?</h2><p>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 <dfn>system/cache</dfn> 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.</p><p>Note: The Benchmark tag is not cached so you can still view your page load speed when caching is enabled.</p><h2>Enabling Caching</h2><p>To enable caching, put the following tag in any of your controller functions:</p><code>$this->output->cache(<var>n</var>);</code><p>Where <var>n</var> is the number of <strong>minutes</strong> you wish the page to remain cached between refreshes.</p><p>The above tag can go anywhere within a function. 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.</p><p class="important"><strong>Warning:</strong> Because of the way CodeIgniter stores content for output, caching will only work if you are generating display for your controller with a <a href="./views.html">view</a>.</p><p class="important"><strong>Note:</strong> Before the cache files can be written you must set the file permissions on your<dfn>system/cache</dfn> folder such that it is writable (666 is usually appropriate, some servers require 777).</p><h2>Deleting Caches</h2><p>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 remove it earlier youwill need to manually delete it from your cache folder.</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://www.codeigniter.com">CodeIgniter</a> &nbsp;&middot;&nbsp; Copyright &#169; 2007 &nbsp;&middot;&nbsp; <a href="http://ellislab.com/">Ellislab, Inc.</a></p></div></body></html>