Cookie vs. Session based flash message

Question

A neat feature which I found in CakePHP was the ability to set a flash message, say on some save script, then have that message displayed on the following page. Something like, Post updated, or Error - no file found.

The way Cake does it is with this session object. I am trying to avoid sessions like the plague because of their odd requirements for scalability. Can I not just simply store the flash message in a cookie (client side) and then delete that cookie once it's displayed on the following page? What would be some pros/cons to this approach - or more simply, why does Cake uses session (I'm assuming that relates to the _SESSION collection).

Cheers!

p.s. In my implementation I also make it fade out with a setTimeout command in javascript. I find that's a nice way to end the whole process.

Answer 1

The problem with a cookie is that the user may disable this functionality. If so, your flash message won't be showed. CakePHP try to be general enough and uses session storage.

You have 3 options:

1. Session: the most used approach. It will work in any client computer but, as you say, it could give problems with some server configurations.
2. Cookies: it's a good option in general, but the user may block this mechanism. Only recommendable when the your app requirements include the need of cookies.
3. Data base: the universal solution. The problem is that it requieres an access to the database (slow). An ID should be passed with the URL (GET method) so the application knows which database register corresponds to this access.

In my applications I use a combination of the 2nd and 3rd approaches: I test for cookies and if they are available, I use them. If not, I use database access, BUT I always cache the DB access in order to not query more than once for each message.