question about cookies slowing down page loads

sfullman

Hi There,

I'm starting to make more use of cookies to save states of windows, default variables, etc. My question is this:

When I write a php script, I have access to any cookie set on that domain by the array $_COOKIE or $HTTP_COOKIE_VARS. Since headers aren't sent out mid-file I suspect, my dear Watson, that when the browser sends a page request to the server, it ALWAYS by default sends out cookies in the header. Is this actually what happens??

If it is, I'd be interested in knowing performance issues. You can have 20 cookies per domain, I think 4096 characters each. A quarter of that is 5x4096=20k over head that gets sent on each page request. That's not too bad but on dial-up connections it would be noticeable (especially going upline vs. down).

Please correct me if I don't understand how this works, or let me know if the performance question is valid.

Thanks,
Sam Fullman
Compass Point Media

[P.S. one more thing -- any way on a per-page basis to supress the browser from sending cookie headers on pages that won't need it? :-)]

nemonoman

4096 bytes is the equivalent of roughly 800 english words. At 150 words per typical manuscript page, that's a cookie that's roughly the equivalent of a 10th Grader's book report.

If you communicated 20, or even 5 4K cookies, I think there would be a performance hit, particularly since upstream data transfer is generally slower than downstream in most user environments. It would be equivalent of uploading 20K-80K files with each browser refresh.

The same performance hit would obtain with POSTING large text-area variables.

I can't imagine saving one 4096 byte cookie, let alone 20. My cookies are about 20 bytes long and handle about 14 tasks.

Personally, I could see ways to make one my cookies 60 or 70 bytes long, but I can't for the life of me guess what I would do with the other 4000 bytes.