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<div class="chapter" title="Chapter 14. Caching">
<div class="titlepage"><div><div><h2 class="title">
<a name="caching"></a>Chapter 14. Caching</h2></div></div></div>
<div class="toc">
<p><b>Table of Contents</b></p>
<dl>
<dt><span class="sect1"><a href="caching.html#caching.setting.up">Setting Up Caching</a></span></dt>
<dt><span class="sect1"><a href="caching.multiple.caches.html">Multiple Caches Per Page</a></span></dt>
<dt><span class="sect1"><a href="caching.groups.html">Cache Groups</a></span></dt>
<dt><span class="sect1"><a href="caching.cacheable.html">Controlling Cacheability of Plugins' Output</a></span></dt>
</dl>
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<p>
Caching is used to speed up a call to <a class="link" href="api.display.html" title="display()"><code class="varname">display()</code></a> or <a class="link" href="api.fetch.html" title="fetch()"><code class="varname">fetch()</code></a> by saving its output
to a file. If a
cached version of the call is available, that is displayed instead of
regenerating the output. Caching can speed things up tremendously,
especially templates with longer computation times. Since the output of
<a class="link" href="api.display.html" title="display()"><code class="varname">display()</code></a> or
<a class="link" href="api.fetch.html" title="fetch()"><code class="varname">fetch()</code></a> is cached,
one cache file could conceivably be made up
of several template files, config files, etc.
</p>
<p>
Since templates are dynamic, it is important to be careful what you are
caching and for how long. For instance, if you are displaying the front page
of your website that does not change its content very often, it might work
well to cache this page for an hour or more. On the other hand, if you are
displaying a page with a timetable containing new information by the
minute, it would not make sense to cache this page.
</p>
<div class="sect1" title="Setting Up Caching">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="caching.setting.up"></a>Setting Up Caching</h2></div></div></div>
<p>
The first thing to do is enable caching by setting <a class="link" href="variable.caching.html" title="$caching">
<em class="parameter"><code>$caching</code></em></a><code class="literal"> = 1 (or 2)</code>.
</p>
<div class="example">
<a name="id3116234"></a><p class="title"><b>Example 14.1. Enabling caching</b></p>
<div class="example-contents"><pre class="programlisting">
<?php
require('Smarty.class.php');
$smarty = new Smarty;
$smarty->caching = 1;
$smarty->display('index.tpl');
?>
</pre></div>
</div>
<br class="example-break"><p>
With caching enabled, the function call to
<code class="literal">display('index.tpl')</code> will render
the template as usual, but also saves a copy of its output to a file (a
cached copy) in the
<a class="link" href="variable.cache.dir.html" title="$cache_dir"><em class="parameter"><code>$cache_dir</code></em></a>.
On the next call to <code class="literal">display('index.tpl')</code>, the cached copy
will be used instead of rendering the template again.
</p>
<div class="note" title="Technical Note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Technical Note</h3>
<p>
The files in the
<a class="link" href="variable.cache.dir.html" title="$cache_dir"><em class="parameter"><code>$cache_dir</code></em></a>
are named similar to the template name.
Although they end in the <code class="filename">.php</code> extention, they are not
intended to be directly executable. Do not edit these files!
</p>
</div>
<p>
Each cached page has a limited lifetime determined by <a class="link" href="variable.cache.lifetime.html" title="$cache_lifetime"><em class="parameter"><code>$cache_lifetime</code></em></a>.
The default value is 3600 seconds ie an hour. After that time expires, the
cache is regenerated. It is possible to give individual caches their own
expiration time by setting
<a class="link" href="variable.caching.html" title="$caching"><em class="parameter"><code>$caching</code></em></a><code class="literal">=2</code>.
See <a class="link" href="variable.cache.lifetime.html" title="$cache_lifetime"><em class="parameter"><code>$cache_lifetime</code></em></a>
for more details.
</p>
<div class="example">
<a name="id3116970"></a><p class="title"><b>Example 14.2. Setting $cache_lifetime per cache</b></p>
<div class="example-contents"><pre class="programlisting">
<?php
require('Smarty.class.php');
$smarty = new Smarty;
$smarty->caching = 2; // lifetime is per cache
// set the cache_lifetime for index.tpl to 5 minutes
$smarty->cache_lifetime = 300;
$smarty->display('index.tpl');
// set the cache_lifetime for home.tpl to 1 hour
$smarty->cache_lifetime = 3600;
$smarty->display('home.tpl');
// NOTE: the following $cache_lifetime setting will not work when $caching = 2.
// The cache lifetime for home.tpl has already been set
// to 1 hour, and will no longer respect the value of $cache_lifetime.
// The home.tpl cache will still expire after 1 hour.
$smarty->cache_lifetime = 30; // 30 seconds
$smarty->display('home.tpl');
?>
</pre></div>
</div>
<br class="example-break"><p>
If <a class="link" href="variable.compile.check.html" title="$compile_check">
<em class="parameter"><code>$compile_check</code></em></a> is enabled,
every template file and config file that is involved with the cache file is
checked for modification. If any of the files have been modified since the
cache was generated, the cache is immediately regenerated. This is a slight
overhead so for optimum performance, set
<a class="link" href="variable.compile.check.html" title="$compile_check"><em class="parameter"><code>$compile_check</code></em>
</a> to <code class="constant">FALSE</code>.
</p>
<div class="example">
<a name="id3117044"></a><p class="title"><b>Example 14.3. Enabling $compile_check</b></p>
<div class="example-contents"><pre class="programlisting">
<?php
require('Smarty.class.php');
$smarty = new Smarty;
$smarty->caching = 1;
$smarty->compile_check = true;
$smarty->display('index.tpl');
?>
</pre></div>
</div>
<br class="example-break"><p>
If <a class="link" href="variable.force.compile.html" title="$force_compile">
<em class="parameter"><code>$force_compile</code></em></a> is enabled,
the cache files will always be regenerated. This effectively turns off
caching.
<a class="link" href="variable.force.compile.html" title="$force_compile"><em class="parameter"><code>$force_compile</code></em>
</a> is usually for
<a class="link" href="chapter.debugging.console.html" title="Chapter 10. Debugging Console">debugging</a>
purposes only, a more efficient way of disabling caching is to set <a class="link" href="variable.caching.html" title="$caching"><em class="parameter"><code>$caching</code></em>
</a><code class="literal"> = 0</code>.
</p>
<p>
The <a class="link" href="api.is.cached.html" title="is_cached()"><code class="varname">is_cached()</code></a>
function
can be used to test if a template has a valid cache or not. If you have a
cached template that requires something like a database fetch, you can use
this to skip that process.
</p>
<div class="example">
<a name="id3117133"></a><p class="title"><b>Example 14.4. Using is_cached()</b></p>
<div class="example-contents"><pre class="programlisting">
<?php
require('Smarty.class.php');
$smarty = new Smarty;
$smarty->caching = 1;
if(!$smarty->is_cached('index.tpl')) {
// No cache available, do variable assignments here.
$contents = get_database_contents();
$smarty->assign($contents);
}
$smarty->display('index.tpl');
?>
</pre></div>
</div>
<br class="example-break"><p>
You can keep parts of a page dynamic with the <a class="link" href="language.function.insert.html" title="{insert}"><code class="varname">{insert}</code></a>
template function. Let's
say the whole page can be cached except for a banner that is displayed down
the side of the page. By using the
<a class="link" href="language.function.insert.html" title="{insert}"><code class="varname">{insert}</code></a>
function for the banner, you
can keep this element dynamic within the cached content. See the
documentation on
<a class="link" href="language.function.insert.html" title="{insert}"><code class="varname">{insert}</code></a>
for more details and examples.
</p>
<p>
You can clear all the cache files with the <a class="link" href="api.clear.all.cache.html" title="clear_all_cache()"><code class="varname">clear_all_cache()</code></a>
function, or
individual cache files
<a class="link" href="caching.groups.html" title="Cache Groups">and groups</a>
with the <a class="link" href="api.clear.cache.html" title="clear_cache()"><code class="varname">clear_cache()</code></a> function.
</p>
<div class="example">
<a name="id3117221"></a><p class="title"><b>Example 14.5. Clearing the cache</b></p>
<div class="example-contents"><pre class="programlisting">
<?php
require('Smarty.class.php');
$smarty = new Smarty;
$smarty->caching = 1;
// clear only cache for index.tpl
$smarty->clear_cache('index.tpl');
// clear out all cache files
$smarty->clear_all_cache();
$smarty->display('index.tpl');
?>
</pre></div>
</div>
<br class="example-break">
</div>
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