Compression and mergin of JS files with PHP- Text editor

Question

I am currently working with minification of JS files for improvement of page speed. I have been able to find the simplest method that works with almost all my js files in exception of two. The problem is with the js files for a wmd editor I am trying to implement to my site. The js files wmd.js and showdown.js are not being compressd and cache by the function in scripts.php. I checked with firebug tool, in the response header of scripts.php neither file is included in the final compressed js file.

What is the issue with my process of compressing these js files(wmd & showdown) and combining it into one? EXAMPLE SITE

js/scripts.php- takes care of compression and cache of js files

<?php
error_reporting(E_ERROR);
// see http://web.archive.org/web/20071211140719/http://www.w3.org/2005/MWI/BPWG/techs/CachingWithPhp
// $lastModifiedDate must be a GMT Unix Timestamp
// You can use gmmktime(...) to get such a timestamp
// getlastmod() also provides this kind of timestamp for the last
// modification date of the PHP file itself
function cacheHeaders($lastModifiedDate) {
    if ($lastModifiedDate) {
        if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) && strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']) >= $lastModifiedDate) {
            if (php_sapi_name()=='CGI') {
                Header("Status: 304 Not Modified");
            } else {
                Header("HTTP/1.0 304 Not Modified");
            }
            exit;
        } else {
            $gmtDate = gmdate("D, d M Y H:i:s \G\M\T",$lastModifiedDate);
            header('Last-Modified: '.$gmtDate);
        }
    }
}

// This function uses a static variable to track the most recent
// last modification time
function lastModificationTime($time=0) {
    static $last_mod ;
    if (!isset($last_mod) || $time > $last_mod) {
        $last_mod = $time ;
    }
    return $last_mod ;
}

lastModificationTime(filemtime(__FILE__));
cacheHeaders(lastModificationTime());
header("Content-type: text/javascript; charset: UTF-8");

ob_start ("ob_gzhandler");

foreach (explode(",", $_GET['load']) as $value) {
    if (is_file("$value.js")) {
        $real_path = mb_strtolower(realpath("$value.js"));
        if (strpos($real_path, mb_strtolower(dirname(__FILE__))) !== false || strpos($real_path, mb_strtolower(dirname(dirname(__FILE__)).DIRECTORY_SEPARATOR.'modules'.DIRECTORY_SEPARATOR)) !== false) {
            lastModificationTime(filemtime("$value.js"));
            include("$value.js");echo "\n";
        } 
    }
}
?>

The way i am calling the compressed.js

<script type = "text/javascript" src = "js/scripts.php?build=12345&load=wmd,showdown"></script>