problem accessing variables of the same form with IIS

Hello, I have a problem accessing variables of the same form that i am in presently. I have text inputs, and the value of this inputs are php variables. with iis, these variables needs to be initialized, now the functionality of my form depends on the user input, now, if i initilized them in the begining then it will be always gets initialied. after the first submittion, everything is fine as i can access the variable using $_REQUEST or _POST, but for the first time when $_REQUEST is nothing i am getting error, for the syntax in the iis, it works fine on Linux. appreciate your help. Thanks Umesh Patel