php预定义变量 （超全局变量）

服务器变量 $_SERVER //count() 34个根据url地址不同，数量有变化

    [REQUEST_URI] => /data1.php
    [DOCUMENT_ROOT] => /var/www/new.so.xywy.com
    [SERVER_PROTOCOL] => HTTP/1.1
    [GATEWAY_INTERFACE] => CGI/1.1
    [SERVER_SOFTWARE] => nginx/1.10.1
    [SERVER_ADDR] => 127.0.0.1
    [HTTP_USER_AGENT] => Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/50.0.2661.102 Chrome/50.0.2661.102 Safari/537.36

http get变量$_GET
http post变量$_POST
request 变量$_REQUEST
环境变量$_ENV
全局变量$_GLOBALS
http文件上传变量$_FILES
http cookies$_COOKIE
session变量$_SESSION