超全局数组
$GLOBALS,$_GET,$_POST,$_REQUEST,$_COOKIE,$_SESSION,$_FILES,
$_ENV(环境变量),$_SERVER(服务器执行环境)
$_SERVER['SERVER_ADDR'] 服务器ip
$_SERVER['SERVER_NAME'] 服务器名称
$_SERVER['REMOTE_ADDR'] 客服端ip
$_SERVER['REQUEST_TIME'] 请求时间
$_SERVER['QUERY_STRING'] ?后面的东西
$_SERVER['PATH_INFO'] ?前一个
$_SERVER['HTTP_REFERER'] 上级请求页面
$_SERVER['HTTP_HOST'] 获得域名