open
read
doRead: invalid sessionId
$_SESSION is not empty

write
doWrite: _symfony_flashes|a:1:{s:3:"foo";a:1:{i:0;s:3:"bar";}}
close
Array
(
    [0] => Content-Type: text/plain; charset=utf-8
    [1] => Cache-Control: max-age=0, private, must-revalidate
    [2] => Set-Cookie: sid=random_session_id; path=/; secure; HttpOnly
)
shutdown