To access the global data which is originating externally, the super globals are used. The superglobals are available as arrays. These superglobals represents the data from URLs, HTML forms, cookies, sessions and also the web server. For this purpose, $HTTP_GET_VARS, $HTTP_POST_VARS are used. The super globals are pretty good enough to be used in functions. The following are the list of super globals.
$_GET, $_POST, $_COOKIE;$_REQUEST, $_SERVER, $_SESSION, $_ENV, $_FILE
Another PHP Superglobal, called $GLOBALS; is available for persisting every variable with global scope.