Why is "Expires" 1981?

Question

My CRON Job returned an error that CRON job did not work. In that this was there:

Set-Cookie: PHPSESSID=2t2drultihqci4em15nbfmeb63; path=/
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache
Content-type: text/html

I am wondering why is Expires set to "1981". What is the significance?

Kite

Personally, I'd put 1984 there, just to screw with people's heads. ;) – Anticholinergic

Why? What's the significance of 1984? – Pengelly

See en.wikipedia.org/wiki/Nineteen_Eighty-Four for a common connotation of 1984 – Plonk

Answer 1

It's an attempt to disable caching.

The date is the birthday of the developer Sascha Schumann who added the code.

From session.c:

Authors: Sascha Schumann <[email protected]> 
         Andrei Zmievski <[email protected]> 

// ...

CACHE_LIMITER_FUNC(private)
{
    ADD_HEADER("Expires: Thu, 19 Nov 1981 08:52:00 GMT");
    CACHE_LIMITER(private_no_expire)(TSRMLS_C);
}

Sotelo

Then happy birthday to him! ;-P – Anticholinergic

Omfg. I could've searched on for hours. - Thanks! See php.net/manual/de/function.session-cache-limiter.php – Cravens

php.net/manual/en/function.session-cache-limiter.php add session_cache_limiter('public') before session_start() to enable caching – Pandemonium

Was Sascha Schumann drunken or what??? Is this the fine art of programming to add private birthdays into Source Code??? – Collimore

@Collimore Why is it a such big problem? – Delatorre

@klenium: Because it is not intuitive! It should be a default Date like: 1.1.1900 etc. Then you not need such a thread. – Collimore

For anyone wanting to see the commit itself, the GitHub commit can be viewed here in the PHP source, committed on Dec 12, 1999: github.com/php/php-src/commit/… – Medea

Answer 2

HTTP Expires header

http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html

It is set to negative or past value, to prevent caching of response.

Quite common usage of this header.

Woorali

Yes...but as I know a session must expire at some point in time(unless I am wrong)....having the expiration date to 1981 how can we achieve that? – Persis

@DimitrisPapageorgiou obviously, session will expire on different terms (and server-side session might last longer than user-side session). Expires header only tells user-browser, to not cache the response and request given URL again, if user requests it. – Woorali

Answer 3

I think you are using session_cache_limiter before calling session_start. If argument is private or no-cache the result is setting the Expires header to the time you have mentioned. Refer to this document for more information.

Linkboy

Answer 4

Somebody just put expires = date('-30 years') (paraphrased) in his code to make really sure the content is set as expired and not cached.

Anticholinergic