Is it possible to delete all the session variables except a few?

Question

Is it possible to delete all the session variables except a few?

I'm building a website using PHP, MySQL

Answer 1

$_SESSION = array_intersect_key($_SESSION, array_flip(array('leave', 'all', 'these', 'keys')));

Answer 2

$dontDelete = array('test1','test2');
foreach($_SESSION as $key => $value) {
   if (!in_array($key,$dontDelete)) {
      unset($_SESSION[$key]);
   }
}