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

to unset a particular session variable use.

unset($_SESSION['one']);

to destroy all session variables at one use.

session_destroy()

To free all session variables use.

session_unset();

if you want to destroy all Session variable except x and y you can do something like this.

$requiredSessionVar = array('x','y');
foreach($_SESSION as $key => $value) {
    if(!in_array($key, $requiredSessionVar)) {
        unset($_SESSION[$key]);
    }
}