PHP + IIS + Windows Authentication. How to find out if a user is logged in using PHP?

Question

PHP

There is a raised IIS with two sites. One accepts requests to an external IP (Internet). The second one is on the internal IP (intranet).
The intranet site has Windows Authentication deployed.
How can you make sure that the user authentication on the site is successful? Is it safe to use server variables [AUTH_USER], [AUTH_TYPE]?

Answer 1

and so:
$user = $_SERVER['LOGON_USER'];
echo "$user";