What is Smarty?
Why use it?
Use Cases and Work Flow
Syntax Comparison
Template Inheritance
Best Practices
Crash Course
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Table of Contents
Caching is used to speed up a call to display()
or fetch()
by saving its output
to a file. If a
cached version of the call is available, that is displayed instead of
regenerating the output. Caching can speed things up tremendously,
especially templates with longer computation times. Since the output of
display()
or
fetch()
is cached,
one cache file could conceivably be made up
of several template files, config files, etc.
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 timetable containing new information by the minute, it would not make sense to cache this page.
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 = 1; $smarty->display('index.tpl'); ?>
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
.
On the next call to display('index.tpl')
, the cached copy
will be used instead of rendering the template again.
The files in the
$cache_dir
are named similar to the template name.
Although they end in the .php
extention, they are not
intended to be directly executable. Do not edit these files!
Each cached page has a limited lifetime determined by $cache_lifetime
.
The default value is 3600 seconds ie an 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'); ?>
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, set
$compile_check
to FALSE
.
Example 14.3. Enabling $compile_check
<?php require('Smarty.class.php'); $smarty = new Smarty; $smarty->caching = 1; $smarty->compile_check = true; $smarty->display('index.tpl'); ?>
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
= 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; $smarty->caching = 1; if(!$smarty->is_cached('index.tpl')) { // No cache available, do variable assignments here. $contents = get_database_contents(); $smarty->assign($contents); } $smarty->display('index.tpl'); ?>
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 side of the page. By using the
{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
and groups
with the clear_cache()
function.
Example 14.5. Clearing the cache
<?php require('Smarty.class.php'); $smarty = new Smarty; $smarty->caching = 1; // clear only cache for index.tpl $smarty->clear_cache('index.tpl'); // clear out all cache files $smarty->clear_all_cache(); $smarty->display('index.tpl'); ?>