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<div class="section" id="web-page-caching">
<h1>Web Page Caching<a class="headerlink" href="#web-page-caching" title="Permalink to this headline">¶</a></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>
<div class="section" id="how-does-caching-work">
<h2>How Does Caching Work?<a class="headerlink" href="#how-does-caching-work" title="Permalink to this headline">¶</a></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 application/cache 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>
</div>
<div class="section" id="enabling-caching">
<h2>Enabling Caching<a class="headerlink" href="#enabling-caching" title="Permalink to this headline">¶</a></h2>
<p>To enable caching, put the following tag in any of your controller
methods:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="nv">$this</span><span class="o">-></span><span class="na">output</span><span class="o">-></span><span class="na">cache</span><span class="p">(</span><span class="nv">$n</span><span class="p">);</span>
</pre></div>
</div>
<p>Where <code class="docutils literal"><span class="pre">$n</span></code> is the number of <strong>minutes</strong> you wish the page to remain
cached between refreshes.</p>
<p>The above tag can go anywhere within a method. It is not affected by
the order that it appears, so place it wherever it seems most logical to
you. Once the tag is in place, your pages will begin being cached.</p>
<div class="admonition important">
<p class="first admonition-title">Important</p>
<p class="last">Because of the way CodeIgniter stores content for output,
caching will only work if you are generating display for your
controller with a <a class="reference internal" href="views.html"><span class="doc">view</span></a>.</p>
</div>
<div class="admonition important">
<p class="first admonition-title">Important</p>
<p class="last">If you change configuration options that might affect
your output, you have to manually delete your cache files.</p>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Before the cache files can be written you must set the file
permissions on your <em>application/cache/</em> directory such that
it is writable.</p>
</div>
</div>
<div class="section" id="deleting-caches">
<h2>Deleting Caches<a class="headerlink" href="#deleting-caches" title="Permalink to this headline">¶</a></h2>
<p>If you no longer wish to cache a file you can remove the caching tag and
it will no longer be refreshed when it expires.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Removing the tag will not delete the cache immediately. It will
have to expire normally.</p>
</div>
<p>If you need to manually delete the cache, you can use the <code class="docutils literal"><span class="pre">delete_cache()</span></code>
method:</p>
<div class="highlight-ci"><div class="highlight"><pre><span></span><span class="c1">// Deletes cache for the currently requested URI</span>
<span class="nv">$this</span><span class="o">-></span><span class="na">output</span><span class="o">-></span><span class="na">delete_cache</span><span class="p">();</span>
<span class="c1">// Deletes cache for /foo/bar</span>
<span class="nv">$this</span><span class="o">-></span><span class="na">output</span><span class="o">-></span><span class="na">delete_cache</span><span class="p">(</span><span class="s1">'/foo/bar'</span><span class="p">);</span>
</pre></div>
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