How to unset/destroy all session data except some specific keys?

Question

I have some session data in a website. I want to destroy all session data when user click another page, except some specific keys like $_SESSION[\'x\'] and

Answer 1

Maybe do something like this

foreach($_SESSION as $key => $val)
{

    if ($key !== 'somekey')
    {

      unset($_SESSION[$key]);

    }

}