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smarty/docs/en/programmers/api-functions/api-is-cached.xml
2006-09-26 23:29:02 +00:00

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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision$ -->
<refentry id="api.is.cached">
<refnamediv>
<refname>is_cached()</refname>
<refpurpose>returns true if there is a valid cache for this template</refpurpose>
</refnamediv>
<refsect1>
<title>Description</title>
<methodsynopsis>
<type>bool</type><methodname>is_cached</methodname>
<methodparam><type>string</type><parameter>template</parameter></methodparam>
<methodparam choice="opt"><type>string</type><parameter>cache_id</parameter></methodparam>
<methodparam choice="opt"><type>string</type><parameter>compile_id</parameter>
</methodparam>
</methodsynopsis>
<itemizedlist>
<listitem><para>
This only works if <link linkend="variable.caching">
<parameter>$caching</parameter></link> is set to &true;, see the
<link linkend="caching">caching section</link> for more info.
</para></listitem>
<listitem><para>
You can also pass a <parameter>$cache_id</parameter> as an optional second
parameter in case you want
<link linkend="caching.multiple.caches">multiple caches</link>
for the given template.
</para></listitem>
<listitem><para>
You can supply a
<link linkend="variable.compile.id"><parameter>$compile id</parameter></link>
as an optional third parameter. If you omit that parameter the persistent
<link linkend="variable.compile.id">
<parameter>$compile_id</parameter></link> is used if its set.
</para></listitem>
<listitem><para>
If you do not want to pass a <parameter>$cache_id</parameter> but want to
pass a <link linkend="variable.compile.id">
<parameter>$compile_id</parameter></link> you have to pass
&null; as a <parameter>$cache_id</parameter>.
</para></listitem>
</itemizedlist>
<note>
<title>Technical Note</title>
<para>
If <varname>is_cached()</varname> returns &true; it actually loads the
cached output and stores it internally. Any subsequent call to
<link linkend="api.display"><varname>display()</varname></link> or
<link linkend="api.fetch"><varname>fetch()</varname></link>
will return this internally stored output and does not try to reload
the cache file. This prevents a race condition that may occur when a
second process clears the cache between the calls to
<varname>is_cached()</varname> and to
<link linkend="api.display"><varname>display()</varname></link>
in the example above. This also means calls to
<link linkend="api.clear.cache"><varname>clear_cache()</varname></link>
and other changes of the cache-settings may have no effect after
<varname>is_cached()</varname> returned &true;.
</para>
</note>
<example>
<title>is_cached()</title>
<programlisting role="php">
<![CDATA[
<?php
$smarty->caching = true;
if(!$smarty->is_cached('index.tpl')) {
// do database calls, assign vars here
}
$smarty->display('index.tpl');
?>
]]>
</programlisting>
</example>
<example>
<title>is_cached() with multiple-cache template</title>
<programlisting role="php">
<![CDATA[
<?php
$smarty->caching = true;
if(!$smarty->is_cached('index.tpl', 'FrontPage')) {
// do database calls, assign vars here
}
$smarty->display('index.tpl', 'FrontPage');
?>
]]>
</programlisting>
</example>
<para>
See also
<link linkend="api.clear.cache"><varname>clear_cache()</varname></link>,
<link linkend="api.clear.all.cache"><varname>clear_all_cache()</varname></link>,
and
<link linkend="caching">caching section</link>.
</para>
</refsect1>
</refentry>
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