I wanted to host an external PHP page in my OSSN document root, linked to from OSSN, but also authenticated using the OSSN session data. I needed to be able to do things not available using custom pages.

Here is how I did it (working source).

Put this at the top of your external page. If they are logged into OSSN, they will be able to access it. If they are not logged into OSSN, they will be returned to your OSSN login page.

I would not rely on this working through future upgrades or new versions though.

<?php

session_start();

if (empty($SESSION["OSSNUSER"])) {
header('Location: http://www.your_ossn_url.com/login');
}

$sessiondata = $SESSION;

$sessiondata = jsondecode(jsonencode($sessiondata), true);

$guid = $sessiondata['OSSNUSER']['guid'];
$firstname = $sessiondata['OSSNUSER']['firstname'];
$lastname = $sessiondata['OSSNUSER']['lastname'];

?>