gistfile1.txt

<?php

class frontendConfiguration extends sfApplicationConfiguration
{

  protected $requestFormat = null;
  
  public function configure()
  {
    $this->dispatcher->connect('request.filter_parameters', array($this, 'filterRequestParameters'));
    $this->dispatcher->connect('view.configure_format', array($this, 'configureIPhoneFormat'));
  }

  public function filterRequestParameters(sfEvent $event, $parameters)
  {
    $request = $event->getSubject();
    if (preg_match('#Mobile/.+Safari#i', $request->getHttpHeader('User-Agent')))
    {
      $this->requestFormat = 'iphone';
    }
    return $parameters;
  }

  public function configureIPhoneFormat(sfEvent $event)
  {
    if ($this->requestFormat == 'iphone')
    {
      //remove
      $event['response']->removeStylesheet('a.css');
      $event['response']->removeJavascript('a.js');
      //add
      $event['response']->addStylesheet('b.css');
      $event['response']->addJavascript('b.js');
    }
  }
}