There are a few ways..
http://example.com/mypage?var1=foo&var2=bar
<?
echo $GET[var1] . $GET[var2]
// results in: foobar
?>
The second method is by using sessions
<?
// page1
session_start();
$HTTP_SESSION_VARS['var1'] = 'foo'
?>
<?
// page 2
session_start();
print_r($HTTP_SESSION_VARS);
?>