How to uniquely identify a computer?

Question

Is there any way to 'grab' some personalized ID, INFO, NAME, NUMBER, DATA, etc.?

Anything just to differentiate and recognize two or more PC on the same IP: something like the Computer name of the user besides $_SESSION?

None of these work:

$hostname = gethostbyaddr($_SERVER['REMOTE_ADDR']);
php_uname('n');
php_uname();

Answer 1

Well, you won't be able to do this from only the HTTP request, but you do have at your disposal the following techniques:

1. Remote Address
2. Cookies/Session
3. User Agent
4. Client-side Web Technologies (e.g. Java or Flash or Silverlight object)

Basically, you can use the concepts of Evercookie to identifiy a client. That being said, why not just use a login system?

Answer 2

No.

(At least not without the users' explicit cooperation.)

Answer 3

There's plenty of information that can be used to create a browser 'fingerprint', but nothing that's guaranteed to be unique. You can find a list of the various data point at the Panopticlick site.