it would require hand coding to evaluate the user group and set a variable with the log out:
Assuming the user group is stored in a session named UserGroup, you could use cold like this on the logout page before the code block to unset the session variables:
<?php
@session_start();
switch ($_SESSION['UserGroup']) {
case "a":
$redir = "page1.php";
break;
case "b":
$redir = "page2.php";
break;
case "c":
$redir = "page3.php";
break;
default:
$redir = "default.php";
}
?>
and this to do the redirect after the code to unset the sessions:
<?php
header("Location: ".$redir); ?>
http://www.php.net/manual/en/control-structures.switch.php