/**
  * 
  * @return EfrontCache
  */
 public static function getInstance()
 {
     if (is_null(self::$_instance)) {
         if (function_exists('apc_store')) {
             self::$_instance = EfrontCache::factory('apc');
         } else {
             if (function_exists('wincache_ucache_set')) {
                 self::$_instance = EfrontCache::factory('wincache');
             } else {
                 self::$_instance = EfrontCache::factory('db');
             }
         }
     }
     return self::$_instance;
 }