Using this plugin you can create a route that pulls values from the current host:

dashboard:
  url:   :username.%APP_HOST%/dashboard/:section
  class: sfHostAwareRoute
  param: { module: dashboard, action: showSection }

The token %APP_HOST% will be replaced with the return value of a call to sfConfig::get('app_host'). You can interpolate any arbitrary config value into the URL in this way.

Your app.yml entries might look something like this:

prod:
  host: domain.com
dev:
  host: domain.localhost

You can then use this route to generate URLs:

<?php echo url_for('@dashboard', array(
  'username' => 'kriswallsmith',
  'section'  => 'account')) ?>

In the dev environment, this will output http://kriswallsmith.domain.localhost/dashboard/account.

When the configured action is called, in this case dashboard/showSection, both the username and section values extracted from the URL will be available as request parameters:

$request->getParameter('username'); // "kriswallsmith"
$request->getParameter('section');  // "account"