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