Description:
------------
session_unset() empties values from all variables in which is $_session stored

Test script:
---------------
<?php
    session_start();
    $_SESSION['test'] = true;
    $var = $_SESSION;
    session_unset();
    print_r($var);

Expected result:
----------------
Array
(
    [test] => 1
)

Actual result:
--------------
Array
(
)