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Multiple Caches Per Page

You can have multiple cache files for a single call to display() or fetch(). Let's say that a call to display('index.tpl') may have several different output contents depending on some condition, and you want separate caches for each one. You can do this by passing a $cache_id as the second parameter to the function call.

Example 14-6. Passing a $cache_id to display()

<?php
require('Smarty.class.php');
$smarty = new Smarty;

$smarty->caching = 1;

$my_cache_id = $_GET['article_id'];

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

Above, we are passing the variable $my_cache_id to display() as the $cache_id. For each unique value of $my_cache_id, a separate cache will be generated for index.tpl. In this example, article_id was passed in the URL and is used as the $cache_id.

Technical Note: Be very cautious when passing values from a client (web browser) into Smarty or any PHP application. Although the above example of using the article_id from the URL looks handy, it could have bad consequences. The $cache_id is used to create a directory on the file system, so if the user decided to pass an extremely large value for article_id, or write a script that sends random article_id's at a rapid pace, this could possibly cause problems at the server level. Be sure to sanitize any data passed in before using it. In this instance, maybe you know the article_id has a length of ten characters and is made up of alpha-numerics only, and must be a valid article_id in the database. Check for this!

Be sure to pass the same $cache_id as the second parameter to is_cached() and clear_cache().

Example 14-7. Passing a cache_id to is_cached()

<?php
require('Smarty.class.php');
$smarty = new Smarty;

$smarty->caching = 1;

$my_cache_id = $_GET['article_id'];

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

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

You can clear all caches for a particular $cache_id by passing NULL as the first parameter to clear_cache().

Example 14-8. Clearing all caches for a particular $cache_id

<?php
require('Smarty.class.php');
$smarty = new Smarty;

$smarty->caching = 1;

// clear all caches with "sports" as the $cache_id
$smarty->clear_cache(null,'sports');

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

In this manner, you can "group" your caches together by giving them the same $cache_id.

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