Doctrine_Cache_Namespaced_Apc.php

<?php
/**
 * This Doctrine Cache Apc class adds a 'prefix' option in order to handle 
 * different APC environments or setups for storing query and cache results
 *
 * @author  Nicolas Perriault
 * @license WTFPL
 */
class Doctrine_Cache_Namespaced_Apc extends Doctrine_Cache_Apc
{
  /**
   * Computes cache key from an id and configured prefix
   *
   * @param  string  $id  cache id
   * @return string
   */
  protected function computeId($id)
  {
    return $this->getOption('prefix').$id;
  }

  /**
   * Fetch a cache record from this cache driver instance
   *
   * @param string $id cache id
   * @param boolean $testCacheValidity    if set to false, the cache validity won't be tested
   * @return mixed  Returns either the cached data or false
   */
  protected function _doFetch($id, $testCacheValidity = true)
  {
    return parent::_doFetch($this->computeId($id), $testCacheValidity);
  }

  /**
   * Test if a cache record exists for the passed id
   *
   * @param string $id cache id
   * @return mixed false (a cache is not available) or "last modified" timestamp (int) of the available cache record
   */
  protected function _doContains($id)
  {
    return parent::_doContains($this->computeId($id));
  }

  /**
   * Save a cache record directly. This method is implemented by the cache
   * drivers and used in Doctrine_Cache_Driver::save()
   *
   * @param string $id    cache id
   * @param string $data    data to cache
   * @param int $lifeTime   if != false, set a specific lifetime for this cache record (null => infinite lifeTime)
   * @return boolean true if no problem
   */
  protected function _doSave($id, $data, $lifeTime = false)
  {
    return parent::_doSave($this->computeId($id), $data, $lifeTime);
  }

  /**
   * Remove a cache record directly. This method is implemented by the cache
   * drivers and used in Doctrine_Cache_Driver::delete()
   *
   * @param string $id cache id
   * @return boolean true if no problem
   */
  protected function _doDelete($id)
  {
    return parent::_doDelete($this->computeId($id));
  }
}

Sample usage, in case it's not clear:

<?php
$cacheDriver = new Doctrine_Cache_Namespaced_Apc(array('prefix' => 'prod')); <- 'prod' should be dynamically set, obviously
$manager = Doctrine_Manager::getInstance();
$manager->setAttribute(Doctrine_Core::ATTR_QUERY_CACHE, $cacheDriver);
$manager->setAttribute(Doctrine_Core::ATTR_QUERY_CACHE_LIFESPAN, 3600);