Beállítottuk $_SESSION['test'] = hello
session_id(): f8e5cda8b2fba583a5697bda39889919
Cookie (from $_COOKIE):
Array
(
    [PHPSESSID] => f8e5cda8b2fba583a5697bda39889919
)
Session content:
Array
(
    [test] => hello
)

Set session to "hello"