除了使用$_SERVER['DOCUMENT_ROOT']之外，是否还有更好的方法返回到目录根目录?

I'm trying to learn a better way to go back to the root directory. I heard that using $_SERVER isn't the safest way. Im wondering if there is a better way. so i could get something like this on the url example.com/exp/my.phpI'm trying to learn a better way to go back to