public function create($type, $config)
    {
        $method = $config->get('Cache.DefinitionImpl');
        if ($method === null) {
            return new HTMLPurifier_DefinitionCache_Null($type);
        }
        if (!empty($this->caches[$method][$type])) {
            return $this->caches[$method][$type];
        }
        if (isset($this->implementations[$method]) &&
            class_exists($class = $this->implementations[$method], false)) {
            $cache = new $class($type);
        } else {
            if ($method != 'Serializer') {
                trigger_error("Unrecognized DefinitionCache $method, using Serializer instead", E_USER_WARNING);
            }
            $cache = new HTMLPurifier_DefinitionCache_Serializer($type);
        }
        foreach ($this->decorators as $decorator) {
            $new_cache = $decorator->decorate($cache);
            // prevent infinite recursion in PHP 4
            unset($cache);
            $cache = $new_cache;
        }
        $this->caches[$method][$type] = $cache;
        return $this->caches[$method][$type];
    }