一些重要的数组
$_COOKIE[] the cookies send by clients
$_ENV[], example $_ENV["HOSTNAME"]
$_FILES[], used for upload files
error, name, size, tmp_name, type. Example $_FILES["formvalue"]["name"]
$_GET[], the values posted by HTTP GET method
$_POST[], the values posted by HTTP POST method
$_REQUEST[], combines _GET, _POST, _COOKIES, _FILES
$SERVER
$_SERVER["DOCUMENT_ROOT"] = /var/www/html
HTTP_ACCEPT = "*/*"
HTTP_ACCEPT_CHARSET
HTTP_ACCEPT_ENCODING
HTTP_ACCEPT_LANGUAGE
HTTP_CONNECTION = Keep-Alive
HTTP_HOST
HTTP_REFERER
HTTP_USER_AGENT
PHP_AUTH_PW
PHP_AUTH_TYPE
PHP_AUTH_USER
PHP_SELF
QUERY_STRING
REMOTE_ADDR
REMOTE_PORT
REQUEST_METHOD
REQUEST_URI
SERVER_ADMIN ( email address )
SERVER_NAME
SERVER_PORT
SERVER_PROTOCOL
SERVER_SIGNATURE // banner of the server
$_SESSION[]