public function load($file)
    {
        $file_name = $this->_config_path.$file.'.php';

        // load the file, but only once
        if (is_file($file_name) and ! array_key_exists($file, $this->_loaded)) {
            // the config file values are secondary to the config values that have already been set
            $this->_config = array_merge(require $file_name, $this->_config);

            $this->_loaded[$file] = true;

            return true;
        } elseif (! is_file($file_name)) {
            throw new \QuickCacheException('The config file "'.$file.'" does not exist');
        }
    }