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smarty/docs/en/programmers/caching/caching-multiple-caches.xml
2006-09-27 00:54:40 +00:00

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<?xml version="1.0" encoding="iso-8859-1"?>
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<sect1 id="caching.multiple.caches">
<title>Multiple Caches Per Page</title>
<para>
You can have multiple cache files for a single call to
<link linkend="api.display"><varname>display()</varname></link>
or <link linkend="api.fetch"><varname>fetch()</varname></link>.
Let's say that a call to <literal>display('index.tpl')</literal> may have
several different output contents depending on some condition, and you want
separate caches for each one. You can do this by passing a
<parameter>$cache_id</parameter> as the second parameter to the
function call.
</para>
<example>
<title>Passing a $cache_id to display()</title>
<programlisting role="php">
<![CDATA[
<?php
require('Smarty.class.php');
$smarty = new Smarty;
$smarty->caching = 1;
$my_cache_id = $_GET['article_id'];
$smarty->display('index.tpl', $my_cache_id);
?>
]]>
</programlisting>
</example>
<para>
Above, we are passing the variable <literal>$my_cache_id</literal> to
<link linkend="api.display"><varname>display()</varname></link>
as the <parameter>$cache_id</parameter>. For each unique value of
<literal>$my_cache_id</literal>, a separate cache will be
generated for <filename>index.tpl</filename>. In this example,
<literal>article_id</literal> was passed in the
URL and is used as the <parameter>$cache_id</parameter>.
</para>
<note>
<title>Technical Note</title>
<para>
Be very cautious when passing values from a client (web browser) into
Smarty or any PHP application. Although the above example of using the
article_id from the URL looks handy, it could have bad consequences. The
<parameter>$cache_id</parameter> is used to create a directory on the file
system, so if the user
decided to pass an extremely large value for article_id, or write a script
that sends random article_id's at a rapid pace, this could possibly cause
problems at the server level. Be sure to sanitize any data passed in before
using it. In this instance, maybe you know the article_id has a length of
ten characters and is made up of alpha-numerics only, and must be a valid
article_id in the database. Check for this!
</para>
</note>
<para>
Be sure to pass the same <parameter>$cache_id</parameter> as the
second parameter to
<link linkend="api.is.cached"><varname>is_cached()</varname></link> and
<link linkend="api.clear.cache"><varname>clear_cache()</varname></link>.
</para>
<example>
<title>Passing a cache_id to is_cached()</title>
<programlisting role="php">
<![CDATA[
<?php
require('Smarty.class.php');
$smarty = new Smarty;
$smarty->caching = 1;
$my_cache_id = $_GET['article_id'];
if(!$smarty->is_cached('index.tpl',$my_cache_id)) {
// No cache available, do variable assignments here.
$contents = get_database_contents();
$smarty->assign($contents);
}
$smarty->display('index.tpl',$my_cache_id);
?>
]]>
</programlisting>
</example>
<para>
You can clear all caches for a particular <parameter>$cache_id</parameter>
by passing &null; as the
first parameter to
<link linkend="api.clear.cache"><varname>clear_cache()</varname></link>.
</para>
<example>
<title>Clearing all caches for a particular $cache_id</title>
<programlisting role="php">
<![CDATA[
<?php
require('Smarty.class.php');
$smarty = new Smarty;
$smarty->caching = 1;
// clear all caches with "sports" as the $cache_id
$smarty->clear_cache(null,'sports');
$smarty->display('index.tpl','sports');
?>
]]>
</programlisting>
</example>
<para>
In this manner, you can <quote>group</quote> your caches together by giving
them the same <parameter>$cache_id</parameter>.
</para>
</sect1>
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