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The Three Cs of Fast CSS and JavaScript

One major "best practice" from both Yahoo! YSlow and Google Page Speed is minimizing HTTP requests. Yahoo! indicates that "80% of the end-user response time is spent on the front end. Most of this time is tied up in downloading all the components in the page: images, stylesheets, scripts, Flash, etc." cite

What does this mean? The fewer calls your page makes to the server, the faster your page is. Here are three ways to drastically improve your site response time:

  • Combine your stylesheets and scripts so that you only have to load one CSS file and one JS file.
  • Compress and minify the combined files so you save bandwidth and transfer time.
  • Cache the compressed output so your server doesn't have to repeat the process for each new visitor.

Here's one way to accomplish this:

<!DOCTYPE html>
<html>
    <head>
        <link rel="stylesheet" type="text/css" href="load.php?type=css">
    </head>
    <body>
        ... website content ...
        <script type="text/javascript" src="load.php?type=js"></script>
    </body>
</html>
<?php
    
    /**
     * The following directory structure is assumed:
     * css/
     *     reset.css
     *     style.css
     * js/
     *     jQuery.js
     *     main.js
     * index.php
     * ...        (the rest of your webpages)
     * load.php   (THIS code block)
     */ 
    
    error_reporting(0);       // supress errors (browsers will see them as invalid CSS/JS)
    ob_start('ob_gzhandler'); // compress with GZIP
    
    $isJavaScript = ($_GET['type'] == 'js');
    if ($isJavaScript) {
        $type = 'javascript'; // content type
        $ext = 'js';          // file extension
        $files = array(       // TODO: modify this list based on your own JS files
            'jQuery',
            'main'
        );
    } else {
        $type = $ext = 'css'; // content type is the same as the extension
        $files = array(       // TODO: modify this list based on your own CSS files
            'reset',
            'style'
        );
    }
    
    header("Content-Type: text/$type"); // set the appropriate content type
    $cache = "$ext/cache.$ext";         // for example, css/cache.css
    if (!file_exists($cache)) {         // see if we've already created a cache
        $toCache = '';
        foreach ($files as $f) {
            $f = "$ext/$f.$ext";        // for example, css/style.css
            if (file_exists($f)) {
                $c = file_get_contents($f);
                if ($isJavaScript) {
                    include_once('jsmin.php');     // get JSMin here
                    $toCache .= JSMin::minify($c); // slow, but only called when there is no cache
                } else {
                    // quick and easy way to minify CSS, removes multiple spaces and blank lines
                    $toCache .= preg_replace(array('/\s\s+/', '/\n/'), array(' ', ' '), $c);
                }
            }
        }
        file_put_contents($cache, $toCache);
    }
    readfile($cache);
    exit;
    
?>

The first time the script is called (ever), it may take a few seconds to generate the cache file, but every time after that it will load extremely quickly due to the "three Cs" implemented above. Since minification is part of the process, you can work directly with unminified and commented code on the server, and let the script minify it for you. If you normally load 3+ stylesheets or scripts, you will see a massive performance boost with this type of script.

If and when you change any of your CSS or JavaScript, just delete the cached file and everything is automatically updated on your site's next visit.

Do you have a favorite method of combining scripts to improve website performance? Please share it in a comment!

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