php - How to uniquely identify a computer? -

is there way 'grab' personalized id, info, name, number, data, etc.?

anything differentiate , recognize 2 or more pc on same ip: computer name of user besides $_session?

none of these work:

$hostname = gethostbyaddr($_server['remote_addr']); php_uname('n'); php_uname(); 

well, won't able http request, have @ disposal 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, can use concepts of evercookie identifiy client. being said, why not use login system?