After I authenticate a user in API how should I make sure they don't have access for too long

I am working on builing an API and application section on a social network so it will be something like myspace, facebook, hi5, friendster, netlog, and many other's have application section, they all use a REST server method and most of them will issue a api key and secret to each application developed. The person who builds the app will pass the api key and a user signature that is created with a hashing algorithm based on the user's ID who is using the app and the apps' API key. The applications code should set a cookie with some information like user id and signature and time. So on my server end the REST part should I just build the signature the same way the app does, check to ma开发者_如何学运维ke sure they are the same, if they are I send the correct data back. My concern is, how do I make sure a developer does not set a user's cookie to keep them authenticated for a long time, should I compare the time the users signature was created and if it is like a day old then I will send a bad response back from the REST?

When a user first add's an application from my main site, I will load the application site into an iframe and I will pass in user ID and other fields where I include the iframe so the application can use GET to initially get the information it needs to set it's cookie.

If you can help on this issue I would appreciate it, does it sound like I am in the right direction so far?

BTW I am using PHp/MySQL

I would store the token & user identifier that you pass back via the API in a database with a timestamp. When the user checks in via API to authenticate, check that timestamp and see if it is too old. If it is then pass back something like FALSE which would trigger some other command to make them re-authenticate into your system, which in turn would generate a new api token for the user to use.

Store a time() value in a session and every time the user does something check that time value to see if it's been longer than X minutes.