CCNA, CCNP, MCSA, CCNA Final Exam, All Answer Test Module With 100/100

Here is my situation. I am writing a program that will store a database. Currently, the way of identifying the user is by their computer user name. I am very desperate here, so any ideas will work. I am looking for ANY method (doesn't always need to work) for BOTH OSX and Windows computers that will somehow fetch the user's first and last name. Thank you all in advance!

I'm making a login page well i've actually finished the login but how would i go about having the web page display diffren't things based on a users privileges and how would i set the privileges in my mysql database? and then use them in my php code?