login related issue

Question

Hi All,

I have login page ,logout page and table column (islogin)
when i click on login button first it check in databse if islogin value is true it show Message User already login if islogin value is false then User can login successfully and update the islogin value true so that only one user can login at time
if click on logout user logout successfully and update the value of islogin false

My problem is

1. if somehow my browser close without click on logout then i am not able login its show user already logged in
manualy i update the table then i am able to login