Media/CDN server w/ Symfony1

filters.yml

# You can find more information about this file on the symfony website:
# http://www.symfony-project.org/reference/1_4/en/12-Filters

rendering: ~

remember_me:
  class: sfGuardRememberMeFilter

security:  ~

# insert your own filters here

mediaServer:
  class: MediaServerFilter

cache:     ~
execution: ~

MediaServerFilter.php

<?php

class MediaServerFilter extends sfFilter
{
    public function execute($filterChain)
    {
        $filterChain->execute();
        // Execute this filter only once
        if ($this->isFirstCall() && sfConfig::get('app_media_filter_disable', false) == false) {
            // Filters don't have direct access to the request and user objects.
            // You will need to use the context object to get them
            $site = dcmsContext::getSite();
            $response = $this->getContext()->getResponse();
            $cont = $response->getContent();
            $host = $site->hostname;
            if (preg_match('/^[a-z0-9]+\.yourdomain\.com/', $host)) {
                $host = preg_replace('/^[0-9a-z]+\./', 'media.', $host);
            }
            $cont = str_replace('"/css/', '"http://' . $host . '/css/', $cont);
            $cont = str_replace('"/js/', '"http://' . $host . '/js/', $cont);
            $cont = str_replace('"/images/', '"http://' . $host . '/images/', $cont);
            $cont = str_replace('url(/media_cache/', 'url(http://' . $host . '/media_cache/', $cont);
            $cont = str_replace('"/media_cache/', '"http://' . $host . '/media_cache/', $cont);
            $cont = str_replace('"/cache/', '"http://' . $host . '/cache/', $cont);
            $cont = str_replace('\'/media_cache/', '\'http://' . $host . '/media_cache/', $cont);
            $cont = str_replace('\'/media/', '\'http://' . $host . '/media/', $cont);
            $cont = str_replace('\'/flash/', '\'http://' . $host . '/flash/', $cont);
            // conflicts with far-future expires.
            //$cont = preg_replace_callback('/'.preg_quote($host).'/', function($matches) { return str_replace('media', 'media'.rand(1, 5), $matches[0]); }, $cont);
            $response->setContent($cont);
        }
    }
}