Multiple Caches Per Page 每页多个缓存

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.
你可以用单个函数display()或fetch()来输出多个缓存文档。display('index.tpl')在多种条件下会有不同的输出内容，要单独的把缓存分开。可以通过函数的第二参数cache_id来达到效果。

Example 14-6. passing a cache_id to display()
例14-6.传给display()一个cache_id

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

$smarty->caching = true;

$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 $my_cache_id, a separate cache will be generated for index.tpl. In this example, "article_id" was passed in the URL and is used as the cache_id.
上面，我们通过变量$my_cache_id作为cache_id来display()。在index.tpl里$my_cache_id的每个唯一值，会建立单独的缓存。在这个例子里，"article_id"在URL传送，并用作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_ids 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 10 characters and is made up of alpha-numerics only, and must be a valid article_id in the database. Check for this!
技术提示：要注意从客户端(web浏览器)传值到Smarty(或任何PHP应用程序)的过程。尽管上面的例子用article_id从URL传值看起来很方便，却可能有糟糕的后果[安全问题]。cache_id被用来在文件系统里创建目录，如果用户想为article_id赋一个很大的值，或写一些代码来快速发送随机的article_ids，就有可能会使服务器出现问题。确定在使用它之前清空已存在的数据。在这个例子，可能你知道article_id的长度(值吧？！)是10字符，并只由字符-数字组成，在数据库里是个可用的article_id。Check for this!要注意检查这个问题！〔要注意这个提示!不用再说了吧？〕

Be sure to pass the same cache_id as the second parameter to is_cached() and clear_cache().
确定传给is_cached()和clear_cache()的第二参数是同一个cache_id。

Example 14-7. passing a cache_id to is_cached()
例14-7.传给is_cached()一个cache_id

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

$smarty->caching = true;

$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().
你可以通过把clear_cache()的第一参数设为null来为特定的cache_id清除所有缓存。

Example 14-8. clearing all caches for a particular cache_id
例14-8.为特定的cache_id清除所有缓存

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

$smarty->caching = true;

// 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.
通过这种方式，你可以用相同的cache_id来把你的缓存集合起来。