The first thing is that register_globals is turned off. This means that to "global" variables you need the [man]Superglobal[/man] arrays. Look up predefined variables. To retrieve a POST variable you need to use $POST, GET use $GET, etc.
Here is an example:
// Get a POST variable named username
$username = $_POST['username'];
// Get a GET variable named pageid
$pageid = $_GET['pageid'];
// Etc.
A really cool way to automatically generate variables that are passed is by using [man]extract[/man].
// Assign all by post variables to themselves
extract($_POST);
// This automatical sets the name->value pair
