How to cache/refresh static resources (server side)

.htaccess

# Default cache values
ExpiresActive ON
ExpiresByType text/html "access plus 1 minute"
ExpiresByType text/css "access plus 1 day"
ExpiresByType text/javascript "access plus 7 days"
ExpiresByType application/x-javascript "access plus 7 days"
ExpiresByType application/javascript "access plus 7 days"
ExpiresByType application/x-shockwave-flash "access plus 7 days"
ExpiresByType image/gif "access plus 1 month"
ExpiresByType image/jpg "access plus 1 month"
ExpiresByType image/png "access plus 1 month"
ExpiresByType image/x-icon "access plus 2 months"

# Rules for versioned static files, ignoring the version number
# Example: assets/js/common.13453234.js
RewriteRule ^(.*)(js|css)/(.+)\.(.+)\.(js|css)$ $1/$2/$3.$5 [L]

header.php

<!-- Method 01 A & B -->
<script type="text/javascript" src="<?php echo site_url(autoVer('assets/js/views/schedule.js')); ?>"></script>
<!-- Method 02 -->
<script type="text/javascript" src="<?php echo site_ver_url('assets/js/views/common.js'); ?>"></script>

MY_url_helper.php

<?php

if ( ! function_exists('autoVer')) {
  /**
   * Method 01 A:
   * Append last modified datetime to filename, .htaccess needs to have the corresponding rule
   * E.g. "assets/css/style.css" converts to "assets/css/style.1363054031.css"
   * @param  $url  String  Relative path
   * @return  String  Modified relative path
   */
  function autoVer($url){
    $path = pathinfo($url);
    $ver = '.' . filemtime($_SERVER['DOCUMENT_ROOT'] . $url) . '.';
    
    return $path['dirname'].'/'.str_replace('.', $ver, $path['basename']);
  }
  
  /**
   * Method 01 B:
   * If your Codeigniter has branch name, e.g. http://www.example.com/dev/assets/css/style.css
   * There'll be an extra step to retrieve the branch name
   * @param  $url  String  Relative path
   * @return  String  Modified relative path
   */
  function autoVer($url){
    $CI =& get_instance();
    
    // Get branch name from base_url config, remove any '/' characters
    $parts = parse_url($CI->config->item('base_url'));
    $branch = strtok($parts['path'], '//');
    
    // Build new file path with version number attached
    $path = pathinfo($url);
    $ver = '.' . filemtime($_SERVER['DOCUMENT_ROOT'] . $branch . '/' . $url) . '.';
    
    return $path['dirname'].'/'.str_replace('.', $ver, $path['basename']);
  }
}

/**
 * Method 02: 
 * Integrate auto-versioning to site_url() of CodeIgniter, cleaner code
 * Supports branch name
 */
if ( ! function_exists('site_ver_url')) {
  function site_ver_url($url) {
    $CI =& get_instance();
    
    // Get branch name, remove any '/' characters
    $parts = parse_url($CI->config->item('base_url'));
    $branch = strtok($parts['path'], '//');
    
    // Build new file path with version number attached
    $path = pathinfo($url);
    $ver = '.' . filemtime($_SERVER['DOCUMENT_ROOT'] . $branch . '/' . $url) . '.';
    
    return site_url($path['dirname'].'/'.str_replace('.', $ver, $path['basename']));
  }
}