Pass Variable Names to a Function

I would like to use a function to check to see if a session variable is set and return the session variable if it is set, and return blank if not. Something like function set_var($var) { echo "var = $var \n"; if (isset($_SESSION['$var']))

    {
    return $_SESSION['$var'];
    }

else

    {
    return "";
    }

} And I would call the function with set_var($name) or set_var($phone). The problem is getting the function to use $var as a variable name, rather than a value. What am I missing, please?

     -----===== Bill =====-----
-- 

Diplomacy - telling your boss he has an open mind
instead of saying he has a hole in his head.