Information we can obtain

[alex_bg]

Hello all,
I wonder what kind of information, except the IP address of a user may be obtained by his single click. I have a poll, and I think that the IP and cookies prevention from people voting twice and more is not enough. So please, tell me, what can I add to the line I use for IP detection, $ip = $HTTP_SERVER_VARS['REMOTE_ADDR'];, so as to gain more information about the computer/else of the voter.
Thank you in advance.

[Mordecai]

$_SERVER["HTTP_USER_AGENT"]. It will return browser information, things like "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)" for IE 6 on Windows XP.

[kevinsequeira]

print_r($HTTP_SERVER_VARS);
or
print_r($_SERVER);

will return the array with all the values

reg
kevin

[alex_bg]

Thank you for the answers, but isn't it possible to obtain specific information about the computer? Something that may surely disclose a fake voter, no matter of him changing browsers and Internet providers (i.e. IPs). A factory number of a component, or...

[Mordecai]

Nope.