How to set Username from Weblogin snippet as nickname in PHPFreeChat?

Hello, i want to integrate PHPFreeChat into my website, but i can’t understand how to set  Username from Weblogin snippet as nickname in PHPFreeChat. It is important to be that users can chat with their Username and that they can’t change nickname at chat.
Thanks. 

Once a web user is logged into your site through modx, you can access the logged user with $_SESSION settings.

$_SESSION[’webShortname’] would give you the username.

thanks, it’s really works 
i’ve just entered

at PHPFreeChat snippet code