$_SERVER 전역 변수
ex) http:// Array ( [DOCUMENT_ROOT] => [HTTP_ACCEPT] => [HTTP_ACCEPT_ENCODING] => [HTTP_ACCEPT_LANGUAGE] => [HTTP_CONNECTION] => [HTTP_COOKIE] => [HTTP_HOST] => [HTTP_UA_CPU] => [HTTP_USER_AGENT] => [PATH] => [REMOTE_ADDR] => [REMOTE_PORT] => [SCRIPT_FILENAME] => [SERVER_ADDR] => [SERVER_ADMIN] => [SERVER_NAME] => [SERVER_PORT] => [SERVER_SIGNATURE] => [SERVER_SOFTWARE] => [GATEWAY_INTERFACE] =>..
