Cache Lite (or Cache_Lite) is a PEAR package that takes the pain out of server-side page caching. If you have a site with more than a moderate amount of traffic, or simply want to ease the server load rendering a particularly complicated PHP page, you should consider using this Cache_Lite.

Caching Overview

Let’s take the example of a real news site I built for a client, McKinneyNews.net. There is a lot going on on the front page: the main body has a story flow that is updated several times a day, blog posts are summarized as needed, and windows to other parts of the site (e.g. calendars & sports schedules) are shown via widgets in the sidebars. All of this dynamic content comes at a huge server performance penalty. Simply put, the home page is expensive to render.

This is where caching comes to the rescue. In the case of news and blog posts, these are updated several times a day, but certainly don’t need to be re-rendered with every page view. In fact, the front page changes perhaps a dozen times a day. Thus we do the heavy lifting in the back-end when content is published, not every time site visitors request the page. On heavy pages like this, caching can decrease load times and improve server performance dramatically.

Cache Lite

When looking for a caching solution, I was concerned with three things: 1) ease of implementation, 2) modularity so it could be used for blocks of content, not just entire pages, and 3) security.

Implementation couldn’t be easier. Simply install the Cache_Lite package (or request that your host install it for you). As a super-user in a terminal, type the following:

pear install Cache_Lite

Now you’re ready to start using Cache_Lite. A very good tutorial on the use of the Cache_Lite package can be found here, but the basic structure is as follows:

<?php
// Include the package
require_once('Cache/Lite.php');

// Set a id for this cache
$id = '123';

// Set a few options
$options = array(

    'cacheDir' => '/tmp/',
    'lifeTime' => 3600

);

// Create a Cache_Lite object
$Cache_Lite = new Cache_Lite($options);

// Test if thereis a valide cache for this id
if ($data = $Cache_Lite->get($id)) {

    // Cache hit !
    // Content is in $data
    // (...)

} else { // No valid cache found (you have to make the page)

    // Cache miss !
    // Put in $data datas to put in cache
    // (...)

    $Cache_Lite->save($data);

}

?>

Since it is a rare case that an entire page is presented to all users identically (e.g. if the page contains a slug that welcomes a user by name), caching only parts of a page becomes a necessity. Instead of using the code above to draw an entire page, use it to draw only a portion of it (e.g. a news block), leaving the other, lighter portions of the page to be rendered dynamically with each page draw.

Likewise, let’s say that the block you want to cache can be drawn one of several, finite ways. Let’s take for example the case where only part of a story is shown to users who are not logged in, while the full story is presented to those who are. If you are not careful, you could cache the whole story and present the logged-in state page to users who are not logged in. The key here is to pick an $id that is unique and state based, and call it back based on that same state.

Finally, security: Cache file corruption because of concurrent read/writes is always a concern, but Cache_Lite takes care of this via hashing and checksums. If the data has been tampered at all or is incomplete due to a write-in-progress, live content is used.

In the time it has taken you to read this article (and thank you for doing so!), you could have Cache_Lite up and running on your site. It’s that simple. Read the documentation (it’s painless) and give it a shot. Your server and your users will thank you for it.

Tags: Cache_Lite, load times, page caching, performance, server load

This entry was posted on Monday, October 22nd, 2007 at 7:00 am and is filed under Recommendations, Tips & Tricks . You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.