WordPress - Combine Javascript Files for fewer HTTP requests

<?php
if( !defined('DS') ) define('DS', DIRECTORY_SEPARATOR);

define('TC_PATH', realpath(dirname(__FILE__)) . DS);

/**
 * Combine CSS/JS File
 *
 * This is used to add the combined file to the $wp_scripts->done property so WordPress
 * knows it has been added already and it also determines the absolute path for the file
 * so it can be accessed via the file system.
 *
 * @filter  tc_combined_js_path Allows filtering of the full js file path.  The filter function
 *                              is passed 3 optional parameters, 'site url' (bloginfo('url')),
 *                              'handle' (the $handle param), and the 'src' value for the script.
 * @filter tc_combined_css_path Allows filtering of the full css file path.  The filter function
 *                              is passed 3 optional parameters, 'site url' (bloginfo('url')),
 *                              'handle' (the $handle param), and the 'src' value for the stylesheet.

 * @param   string  $handle     The script/stylesheet's handle it was registered with.
 * @param   string  $type       Valid values are 'css' or 'js'.  This determines which
 *                              type of file we're adding.
 * @return  string              The full path to the file, if it could be determined,
 *                              (bool)false otherwise.
 * @access  private
 */
function _tc_add_combine_file( $handle, $type )
{
    if( $type != 'js' && $type != 'css' ) {
        trigger_error('Invalid file type given!  Must be `css` or `js`.');
        return false;
    }

    $siteurl = get_bloginfo('url');

    if( $type == 'js' )
    {
        global $wp_scripts;
        // Strip the site URL from the file so we can determine it's path ...
        $uri  = ltrim(str_replace($siteurl, '', $wp_scripts->registered[$handle]->src), '/');
        $path = realpath(ABSPATH . DS . $uri);
        $path = apply_filters('tc_combine_js_path', $path, $siteurl, $handle, $wp_scripts->registered[$handle]->src);

        // Only add it to the done queue if a path was found, this way we don't break the theme...
        if( $path )
            $wp_scripts->done[] = $handle;
    }
    else
    {
        global $wp_styles;
        $uri  = ltrim(str_replace($url, '', $wp_styles->registered[$handle]->src), '/');
        $path = realpath(ABSPATH . DS . $uri);
        $path = apply_filters('tc_combine_css_path', $path, $siteurl, $handle, $wp_styles->registered[$handle]->src);

        if( $path )
            $wp_styles->done[] = $handle;
    }
    return $path;
}

/**
 * Recursive Combine JS Dependencies
 *
 * A function used by _tc_combine_js() to recursively add queued script's dependencies
 * and perform any that are excluded from the combined JS file.
 *
 * @param   string  $hdl        The queued script handle to process the dependencies for.
 * @param   object  $wp_scripts The WP_Scripts object, passed by reference.
 * @param   array   $exclude    An array of script handles to exclude from the combined file.
 * @return  array               An array of all of the dependencies that are included in the combined JS.
 * @access  private
 */
function _tc_recursive_deps( $hdl, &$wp_scripts, $exclude )
{
    $files = array();

    foreach($wp_scripts->registered[$hdl]->deps as $dep)
    {
        if( count($wp_scripts->registered[$dep]->deps) )
        {
            $files = array_merge($files, _tc_recursive_deps($dep, $wp_scripts, $exclude));
        }
        else
        {
            // If the dependency is in the excluded array, we must go ahead and add it
            // so the scripts depending on it won't break.
            if( in_array($dep, $exclude) ) {
                $wp_scripts->do_items(array($dep));
                continue;
            }
            // Make sure the dependency isn't in the 'done' array so we don't add it twice
            elseif( !in_array($dep, $wp_scripts->done) ) {
                $path = _tc_add_combine_file( $dep, 'js' );
                if( $path ) $files[] = $path;
            }
        }
    }
    // Finally, if the passed queue is in the exclude array, we have to go ahead and add it
    // as well, for the same reason mentioned above.
    if( in_array($hdl, $exclude) ) {
        $wp_scripts->do_items(array($dep));
    }
    else
    {
        $path = _tc_add_combine_file( $hdl, 'js' );
        if( $path ) $files[] = $path;
    }
    return $files;
}

/**
 * Combine JS Files
 *
 * This combines all of the Javascript files that have been registered/enqueued via
 * WordPress's script queueing system.
 *
 * The filter 'tc_combine_js' allows for exclusions of specific files.
 * Files are grouped together into two groups, header JS and footer JS, this way
 * they still load in the correct places.
 *
 * @param   void
 * @return  void
 * @access  private
 */
function _tc_combine_js()
{
    global $wp_scripts;
    $footer   = array();
    $header   = array();
    $cachefor = apply_filters('tc_combine_js_cache_for', 60*60);
    // Specify any scripts by handle that should be excluded from the combined JS
    $exclude = apply_filters('tc_combine_js_exclude', array('admin-bar'));

    // First process the header Javascripts
    foreach($wp_scripts->queue as $queue)
    {
        $curqueue = $wp_scripts->registered[$queue];

        // Skip footer scripts and just process header scripts for now...
        if(isset($curqueue->extra['group']) && $curqueue->extra['group'] == '1')
            continue;
        // Recursively add all dependencies
        $header = array_merge($header, _tc_recursive_deps($queue, $wp_scripts, $exclude));
    }
    $header = apply_filters('tc_header_combine_js', $header);

    // Now process the footer Javascripts
    foreach($wp_scripts->queue as $queue)
    {
        if( in_array($queue, $wp_scripts->done) ) continue;

        $footer = array_merge($footer, _tc_recursive_deps($queue, $wp_scripts, $exclude));
    }
    $footer = apply_filters('tc_footer_combine_js', $footer);

    // Use converted MD5 hash to verify all files are included since someone logged in
    // might have different JS that loads than someone who isn't, etc.
    $file_hash    = base_convert(md5(implode('', $header)), 10, 36);

    $headjs_cache = apply_filters('tc_headjs_cache_file', 'hjs.cache.'. $file_hash .'.js', $file_hash);

    // Determine if we need to create a new cached header js file or not.
    if( !file_exists(TC_PATH . $headjs_cache) || (filemtime(TC_PATH . $headjs_cache)+intval($cachefor)) < time() )
    {
        $hdl = fopen(TC_PATH . $headjs_cache, "w");

        foreach($header as $file)
        {
            if( !file_exists($file) )
                trigger_error('File `'. $file .'` does not exist!', E_USER_WARNING);
            else
                fwrite($hdl, file_get_contents($file));
        }
        fclose($hdl);
    }

    $file_hash    = base_convert(md5(implode('', $footer)), 10, 36);
    $footjs_cache = apply_filters('tc_footjs_cache_file', 'fjs.cache.'. $file_hash .'.js', $file_hash);

    // Determine if we need to create a new cached footer js file or not.
    if( !file_exists(TC_PATH . $footjs_cache) || (filemtime(TC_PATH . $footjs_cache)+intval($cachefor)) < time() )
    {
        $hdl = fopen(TC_PATH . $footjs_cache, "w");

        foreach($footer as $file)
        {
            if( !file_exists($file) )
                trigger_error('File `'. $file .'` does not exist!', E_USER_WARNING);
            else
                fwrite($hdl, file_get_contents($file));
        }
        fclose($hdl);
    }

    // Form the URLs and correct slashes for valid URLs.
    $hjs_url = get_bloginfo('template_directory') .'/'. str_replace('\\', '/', $headjs_cache);
    $fjs_url = get_bloginfo('template_directory') .'/'. str_replace('\\', '/', $footjs_cache);

    wp_enqueue_script('hjs-cache', $hjs_url);
    wp_enqueue_script('fjs-cache', $fjs_url, false, '', true);
}

if( !is_admin() ) add_action('wp_print_scripts', '_tc_combine_js');

/////////////////
// Filter Test
/////////////////
function removeit($excluded) {
    return array_merge($excluded, array('jquery'));
}
add_filter('tc_combine_js_exclude', 'removeit', 10, 1);