这段代码如何理解

private static function parse_conf(&$setting_config){		$nc_config = $GLOBALS['config'];		if(is_array($nc_config['db']['slave']) && !empty($nc_config['db']['slave'])){			$dbslave = $nc_config['db']['slave'];			$sid     = array_rand($dbslave);			$nc_config['db']['slave'] = $dbslave[$sid];		}else{			$nc_config['db']['slave'] = $nc_config['db'][1];		}		$nc_config['db']['master'] = $nc_config['db'][1];		$setting_config = $nc_config;		$setting = ($setting = rkcache('setting')) ? $setting : rkcache('setting',true);		$setting['shopnc_version'] = '<span class="vol"><font class="b">E-</font><font class="o">Mall</font></span>';		$setting_config = array_merge_recursive($setting,$nc_config);	}