PHP Notice: Undefined index: HTTP_HOST

PHP Notice: Undefined index: HTTP_HOST  看php错误日志， 阿帕奇错误日志一样都有这个，虽然无伤大雅，但是还是咨询下

我就问下是不是 https造成的，据我所知 HTTP_HOST 并不是一定存在的，我还特意看了下别人的答案  

It's only set for named vhosts specifically. If you access localhost as default server using HTTP/1.0 sans Host: header, then it's absent. Obviously also for cron/cmdline invocation


是不是加个    if (isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] == 'on')  判断比较好？