I have custom php script located inside pub/. It doesn't use Magento objects to limit spent resources because it is called at each page load with ajax call.
Inside that script I need to check if data saved to cookie inside Magento observer is from the same Magento session or not.
In Magento 1 it was easy by using
$_COOKIE['frontend']. Each time I saved data to cookie I also saved information about $_COOKIE['frontend']. When I read cookie value I also checked if
$_COOKIE['frontend'] is still the same as it was when I saved the cookie information.
Now with Magento 2 there is no cookie with name frontend, I found useful cookies just cookie
PHPSESSID, but this is probably not the same as Magento session id. At least with Magento 1 it was different, it could last different time as Magento session id. So how does Magento 2 check Magento session id, is in Magento 2 the same as