Evert Pot has a quick new post to his blog today talking about how to push encrypted information into a cookie for storage.

There have been a couple of approaches I've been considering [to replace sessions being stored in the database], one of which is simply storing all the information in a browser cookie. First I want to make clear I don't necessarily condone this. The reason I'm writing this post, is because I'm hoping for some more community feedback. Is this a really bad idea? I would love to know.

He includes some code to make it happen - a class that uses the hash_hmac function and a SHA1 encryption type (along with a salt) to convert the information into a string that can be (relatively) safely stored in a cookie. Be sure to read the comments for more opinions on the method.