Unsetting a session variable sometimes does not work with http and https

I am getting problem in using session variable. In chrome it's working but in Mozilla some time session data is being removed automatically.

I have tried all the way which i have gotten after search. But still I am getting problem. only some data from array is being removed.

I am using 5 form all form is placed on different pages. And all data is being saved in session. So, in some case some field value is being lost.

I have tried to change session variable in php.ini . I have also used ini_set('session.gc_probability', 1); ini_set('session.gc_divisor', 100); ini_set('session.gc_maxlifetime', 200000); ini_set('session.cookie_lifetime', 0); $conf['https'] = FALSE; I have used these variable in setting.php . I have made simple form using form api. After submit I am saving value in session. So, in some case some value is being missed when i goes onto another page.