Before you turn them on, you should probably consider whether you really need them on. They are turned off by default to prevent potential security risks introduced by bad PHP programming.
You'd probably be better off just adding these lines to the top of the script:
$page = $REQUEST['page'];
$id = $REQUEST['id'];
$change = $REQUEST['change'];
$type = $REQUEST['type'];
That's the best way - the right way - to write your PHP scripts.
Or, you can defeat the whole point of turning Globals off by adding this to the top of your script:
foreach ($_REQUEST as $k=>$v) { $$k = $v; }
But, again, that defeats the whole point of turning Globals off as a security precaution.
Or, if you really really want Globals turned on, you can make the change in your php.ini file if you have access to it.