<?php

/*
 * .htaccess 
 * <IfModule mod_rewrite.c>
 *        RewriteEngine on
 *      RewriteCond %{REQUEST_FILENAME} !-d
 *       RewriteCond %{REQUEST_FILENAME} !-f
 *       RewriteRule ^(.*)\.(.+)\.(css|js)$ $1.$3 [L] # Strip out the version number
 * </IfModule>
 *
 */
 
 /* 
  * timestamp to base64 shortner
  */
 function shorten($id, $alphabet='0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-')
{
    $base = strlen($alphabet);
    $short = '';
    while($id) {
        $id = ($id-($r=$id%$base))/$base;
        $short = $alphabet{$r} . $short;
    };
    return $short;
}

/**
 *  Given a file, i.e. /css/base.css, replaces it with a string containing the
 *  file's mtime, i.e. /css/base.1221534296.css.
 *  
 *  @param $file  The file to be loaded.  Must be an absolute path (i.e.
 *                starting with slash).
 */
function auto_version($file)
{
  if(strpos($file, '/') !== 0 || !file_exists($_SERVER['DOCUMENT_ROOT'] . $file))
    return $file;

  $mtime = filemtime($_SERVER['DOCUMENT_ROOT'] . $file);
  $short = shorten($mtime);

  return preg_replace('{\\.([^./]+)$}', ".$short.\$1", $file);
}

//this function should be called where ever we include the static files, like in common header.php
echo auto_version('/js/jquery.js');

?>