PHP Predefined Variables

* Superglobals — Superglobals are built-in variables that are always available in all scopes

* $GLOBALS — References all variables available in global scope

* $_SERVER — Server and execution environment information

* $_GET — HTTP GET variables

* $_POST — HTTP POST variables

* $_FILES — HTTP File Upload variables

* $_REQUEST — HTTP Request variables

* $_SESSION — Session variables

* $_ENV — Environment variables

* $_COOKIE — HTTP Cookies

* $php_errormsg — The previous error message

* $HTTP_RAW_POST_DATA — Raw POST data

* $http_response_header — HTTP response headers

* $argc — The number of arguments passed to script

* $argv — Array of arguments passed to script