Use-case: caching module's configuration

docs/cache.md

@@ -47,8 +47,43 @@ In this case you have to specify a custom factory in your `service_manager` conf
 ),
 ```
 
+Please be aware that you can't use *Closures* inside yout module configuration if you want to cache it. To avoid this problem, you have to use a Factory:
+```php
+// module.config.php
+'service_manager' => array(
+    'factories' => array(
+        'my_memcached_alias' => __NAMESPACE__ . '\Cache\MemcachedFactory'
+    )
+),
+```
+
+```php
+// MemcachedFactory.php
+namespace YourModule\Cache;
+
+use Zend\ServiceManager\FactoryInterface;
+use Zend\ServiceManager\ServiceLocatorInterface;
+
+class MemcachedFactory implements FactoryInterface {
+
+    /**
+     * @param ServiceLocatorInterface $serviceLocator
+     *
+     * @return \Memcached
+     */
+    public function createService(ServiceLocatorInterface $serviceLocator) {
+
+        $memcached = new \Memcached();
+        $memcached->addServer('localhost', 11211);
+        return $memcached;
+    }
+
+}
+```
+
+
 Other supported that need a custom factory are:
 
 * `memcache`: require you to return a `Memcache` instance (use the `my_memcache_alias` as the key in the
 service manager).
-* `redis`: require you to return a `Redis` instance (use the `my_redis_alias` as the key in the service manager).
+* `redis`: require you to return a `Redis` instance (use the `my_redis_alias` as the key in the service manager).