Getting windows username into php/mysql

HI, I have been searching the internet for days trying to find a way of getting the windows username (%username%) of the current logged on user and submitting it, along side some other information (entered into the form by the user), to a MysQl database. This will enable me to know who has submitted the form on my intranet. I have quite a bit of php/mysql knowledge, and i know the windows variable is %username% (easy i know) i just dont know how to get the variable into an array so i can post it to mysql db Any help would be great as im all out of place to look.... Thanks in advance