Get the Result Cache from the doctrine entity manager

doctrine_cache_driver.php

<?php

class Foo
{
    private $_em;

    public function __construct($entity_manager)
    {
        $this->_em = $entityManager; 
    }

    /**
     * I couldn't find any where in the Doctrine or Symfony docs that explained
     * how to get the Cache Driver defined in my config_prod.yml file for use
     * in saving custom arrays/keys.
     *
     * (Rather than directly instantiating a cache driver i.e. $cacheDriver = new \Doctrine\Common\Cache\ApcCache())
     *
     * @return Implementation of Doctrine\Common\Cache\Cache (APC/Xcache etc.)
     */
    public function getCacheDriver()
    {
        return $this->_em->getConfiguration()->getResultCacheImpl();
    }

    /**
     * Example usage of Foo::getCacheDriver
     * 
     */
    public function saveToCache($item_to_save)
    {
        $this->getCacheDriver()->save('foo_key', $item_to_save);
    }
}

$foo = new Foo($doctrine_entity_manager);

$foo->saveToCache('bar');