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<td><h1>CodeIgniter User Guide Version 1.7.1</h1></td>
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<a href="http://codeigniter.com/">CodeIgniter Home</a> ›
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<a href="../index.html">User Guide Home</a> ›
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Page Caching
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<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 <input type="text" class="input" style="width:200px;" name="q" id="q" size="31" maxlength="255" value="" /> <input type="submit" class="submit" name="sa" value="Go" /></form></td>
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<h1>Web Page Caching</h1>
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<p>CodeIgniter lets you cache your pages in order to achieve maximum performance.</p>
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<p>Although CodeIgniter is quite fast, the amount of dynamic information you display in your pages will correlate directly to the
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server resources, memory, and processing cycles utilized, which affect your page load speeds.
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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>
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<h2>How Does Caching Work?</h2>
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<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.
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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
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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>
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<p>Note: The Benchmark tag is not cached so you can still view your page load speed when caching is enabled.</p>
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<h2>Enabling Caching</h2>
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<p>To enable caching, put the following tag in any of your controller functions:</p>
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<code>$this->output->cache(<var>n</var>);</code>
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<p>Where <var>n</var> is the number of <strong>minutes</strong> you wish the page to remain cached between refreshes.</p>
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<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
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most logical to you. Once the tag is in place, your pages will begin being cached.</p>
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<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>
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<p class="important"><strong>Note:</strong> Before the cache files can be written you must set the file permissions on your
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<dfn>system/cache</dfn> folder such that it is writable.</p>
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<h2>Deleting Caches</h2>
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<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:
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Removing the tag will not delete the cache immediately. It will have to expire normally. If you need to remove it earlier you
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will need to manually delete it from your cache folder.</p>
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<a href="#top">Top of Page</a> ·
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