smarty/docs/ru/programmers/caching/caching-setting-up.xml

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   <sect1 id="caching.setting.up">
   <title>Setting Up Caching</title>
   <para>
   The first thing to do is enable caching. This is done by setting <link
   linkend="variable.caching">$caching</link> = true (or 1.)     
   </para>
    <example>
     <title>enabling caching</title>
     <programlisting>
require('Smarty.class.php');
$smarty = new Smarty;

$smarty->caching = true;

$smarty->display('index.tpl');</programlisting>
    </example>
	<para>
	With caching enabled, the function call to display('index.tpl') will render
	the template as usual, but also saves a copy of its output to a file (a
	cached copy) in the <link linkend="variable.cache.dir">$cache_dir</link>.
	Upon the next call to display('index.tpl'), the cached copy will be used
	instead of rendering the template again.
	</para>
	<note>
	<title>Technical Note</title>
	<para>
	The files in the $cache_dir are named similar to the template name.
	Although they end in the ".php" extention, they are not really executable
	php scripts. Do not edit these files!
	</para>
	</note>
	<para>
	Each cached page has a limited lifetime determined by <link
	linkend="variable.cache.lifetime">$cache_lifetime</link>. The default value
	is 3600 seconds, or 1 hour. After that time expires, the cache is
	regenerated. It is possible to give individual caches their own expiration
	time by setting $caching = 2. See the documentation on <link
	linkend="variable.cache.lifetime">$cache_lifetime</link> for details.
	</para>
    <example>
     <title>setting cache_lifetime per cache</title>
     <programlisting>
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
$smarty->display('home.tpl');</programlisting>
    </example>
	<para>
	If <link linkend="variable.compile.check">$compile_check</link> 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, leave $compile_check set to false.
	</para>
    <example>
     <title>enabling $compile_check</title>
     <programlisting>
require('Smarty.class.php');
$smarty = new Smarty;

$smarty->caching = true;
$smarty->compile_check = true;

$smarty->display('index.tpl');</programlisting>
	</example>
	<para>
	If <link linkend="variable.force.compile">$force_compile</link> is enabled,
	the cache files will always be regenerated. This effectively turns off
	caching. $force_compile is usually for debugging purposes only, a more
	efficient way of disabling caching is to set <link
	linkend="variable.caching">$caching</link> = false (or 0.)
	</para>
	<para>
	The <link linkend="api.is.cached">is_cached()</link> 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.
	</para>
    <example>
     <title>using is_cached()</title>
     <programlisting>
require('Smarty.class.php');
$smarty = new Smarty;

$smarty->caching = true;

if(!$smarty->is_cached('index.tpl')) {
	// No cache available, do variable assignments here.
	$contents = get_database_contents();
	$smarty->assign($contents);
}

$smarty->display('index.tpl');</programlisting>
    </example>
	<para>
	You can keep parts of a page dynamic with the <link
	linkend="language.function.insert">insert</link> template function. Let's
	say the whole page can be cached except for a banner that is displayed down
	the right side of the page. By using an insert function for the banner, you
	can keep this element dynamic within the cached content. See the
	documentation on <link linkend="language.function.insert">insert</link> for
	details and examples.
	</para>
	<para>
	You can clear all the cache files with the <link
	linkend="api.clear.all.cache">clear_all_cache()</link> function, or
	individual cache files (or groups) with the <link
	linkend="api.clear.cache">clear_cache()</link> function.	
	</para>
    <example>
     <title>clearing the cache</title>
     <programlisting>
require('Smarty.class.php');
$smarty = new Smarty;

$smarty->caching = true;

// clear out all cache files
$smarty->clear_all_cache();

// clear only cache for index.tpl
$smarty->clear_cache('index.tpl');

$smarty->display('index.tpl');</programlisting>
    </example>
</sect1>
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