smarty/docs/en/programmers/advanced-features/section-template-cache-handler-func.xml

<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision$ -->
  <sect1 id="section.template.cache.handler.func">
   <title>Cache Handler Function</title>
   <para>
    As an alternative to using the default file-based caching mechanism, you
    can specify a custom cache handling function that will be used to
    <literal>read</literal>, <literal>write</literal> and
    <literal>clear</literal> cached files.
   </para>
   <para>
    Create a function in your application that Smarty will use as a
    cache handler. Set the name of it in the
    <link linkend="variable.cache.handler.func">
    <parameter>$cache_handler_func</parameter></link>
    class variable. Smarty will now use this to handle cached data.
    </para>

    <itemizedlist>
    <listitem><para>
    The first argument is the action, which will be one of
    <literal>read</literal>, <literal>write</literal> and
    <literal>clear</literal>.
    </para></listitem>

    <listitem><para>
    The second parameter is the Smarty object.
    </para></listitem>

    <listitem><para>The third parameter
    is the cached content. Upon a <literal>write</literal>, Smarty passes the
    cached content  in these parameters. Upon a <literal>read</literal>,
    Smarty expects your function to accept this parameter by reference and
    populate it with the cached data. Upon a <literal>clear</literal>, pass a
    dummy variable here since it is not used.
    </para></listitem>

    <listitem><para>
    The fourth parameter is the <parameter>name</parameter> of the template
    file, needed for read/write.
    </para></listitem>

    <listitem><para>
    The fifth parameter is the optional <parameter>$cache_id</parameter>.
    </para></listitem>

    <listitem><para>
    The sixth is the optional <link linkend="variable.compile.id">
    <parameter>$compile_id</parameter></link>.
    </para></listitem>

    <listitem><para>
    The seventh and last parameter <parameter>$exp_time</parameter>
    was added in Smarty-2.6.0.
   </para></listitem>

   </itemizedlist>

   <example>
    <title>Example using MySQL as a cache source</title>
    <programlisting role="php">
<![CDATA[
<?php
/**************************************************
example usage:

include('Smarty.class.php');
include('mysql_cache_handler.php');

$smarty = new Smarty;
$smarty->cache_handler_func = 'mysql_cache_handler';

$smarty->display('index.tpl');


mysql database is expected in this format:

create database SMARTY_CACHE;

create table CACHE_PAGES(
CacheID char(32) PRIMARY KEY,
CacheContents MEDIUMTEXT NOT NULL
);

**************************************************/

function mysql_cache_handler($action, &$smarty_obj, &$cache_content, $tpl_file=null, $cache_id=null, $compile_id=null, $exp_time=null)
{
	// set db host, user and pass here
	$db_host = 'localhost';
	$db_user = 'myuser';
	$db_pass = 'mypass';
	$db_name = 'SMARTY_CACHE';
	$use_gzip = false;

	// create unique cache id
	$CacheID = md5($tpl_file.$cache_id.$compile_id);

	if(! $link = mysql_pconnect($db_host, $db_user, $db_pass)) {
		$smarty_obj->_trigger_error_msg('cache_handler: could not connect to database');
		return false;
	}
	mysql_select_db($db_name);

	switch ($action) {
		case 'read':
			// read cache from database
			$results = mysql_query("select CacheContents from CACHE_PAGES where CacheID='$CacheID'");
			if(!$results) {
				$smarty_obj->_trigger_error_msg('cache_handler: query failed.');
			}
			$row = mysql_fetch_array($results,MYSQL_ASSOC);

			if($use_gzip && function_exists('gzuncompress')) {
				$cache_content = gzuncompress($row['CacheContents']);
			} else {
				$cache_content = $row['CacheContents'];
			}
			$return = $results;
			break;
		case 'write':
			// save cache to database

			if($use_gzip && function_exists("gzcompress")) {
				// compress the contents for storage efficiency
				$contents = gzcompress($cache_content);
			} else {
				$contents = $cache_content;
			}
			$results = mysql_query("replace into CACHE_PAGES values(
							'$CacheID',
							'".addslashes($contents)."')
						");
			if(!$results) {
				$smarty_obj->_trigger_error_msg('cache_handler: query failed.');
			}
			$return = $results;
			break;
		case 'clear':
			// clear cache info
			if(empty($cache_id) && empty($compile_id) && empty($tpl_file)) {
				// clear them all
				$results = mysql_query('delete from CACHE_PAGES');
			} else {
				$results = mysql_query("delete from CACHE_PAGES where CacheID='$CacheID'");
			}
			if(!$results) {
				$smarty_obj->_trigger_error_msg('cache_handler: query failed.');
			}
			$return = $results;
			break;
		default:
			// error, unknown action
			$smarty_obj->_trigger_error_msg("cache_handler: unknown action \"$action\"");
			$return = false;
			break;
	}
	mysql_close($link);
	return $return;

}

?>
]]>
</programlisting>
    </example>
</sect1>
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