Session Syntax

There are a few syntaxs in php for registering and accessing session vars the old way was
var $foo;
session_register('foo');
$HTTP_SESSION_VARS['foo'];

the new way is

$_SESSION['bar'] = $foo;
echo $_SESSION['bar']

The new way seems not to work in my implementation os osC which is strange becuase we are using PHP ver.4.3.4

The oscommerce way

var $foo;
tep_session_register('foo')

to access you just
echo $foo;

which makes the least sense out of all 3.