Access Log Missing Authenticated Users

["Liz Kim" <lizkim270@xxxxxxxxx>]

I have a directory which is password protected.
When a user tries to access this pw protected area, the access log keeps track of the access in the following format:
USER_IP_ADDRESS - USERNAME - [DATE: TIME] HTTP REQUEST

However, when I added a PHP script within this script as the index file and created a session,
The username field just appears blank.

Is there a way to log the username while using php with sessions?

Thanks,
LK