How to clear only one variable in the session in php

I am developing application which is having lots of session variables in php. I am even using login details in the session too, what i want is to clear few variables but keep my login details in the session, how can i clear particular session variable and not all?

 

You do either this:

$_SESSION['watever'] = "";

PHP:

Or this:

unset($_SESSION['watever']);

PHP: