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 weather map containing new information by the
minute, it would not make sense to cache this page.
Setting Up Caching
The first thing to do is enable caching by setting $caching = 1 (or 2).
Example 14-1. enabling caching
<?php
require('Smarty.class.php');
$smarty = new Smarty;
$smarty->caching = true;
$smarty->display('index.tpl');
?>
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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 $cache_dir.
Upon the next call to display('index.tpl'), the cached copy will be used
instead of rendering the template again.
Technical Note:
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!
Each cached page has a limited lifetime determined by $cache_lifetime. 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 $cache_lifetime for more details.
Example 14-2. setting $cache_lifetime per cache
<?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');
?>
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If $compile_check 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.
Example 14-3. enabling $compile_check
<?php
require('Smarty.class.php');
$smarty = new Smarty;
$smarty->caching = true;
$smarty->compile_check = true;
$smarty->display('index.tpl');
?>
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If $force_compile 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 $caching = false (or 0.)
The is_cached() 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.
Example 14-4. using is_cached()
<?php
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');
?>
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You can keep parts of a page dynamic with the {insert} 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 {insert} for
more details and examples.
You can clear all the cache files with the clear_all_cache() function, or
individual cache files
(or groups)
with the clear_cache() function.
Example 14-5. clearing the cache
<?php
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');
?>
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