Include the file before all other code (or make available to your custom autoload). You can then protect your sessions with:
new Session_Security;
The object stores the fingerprint information in the session under key "fingerprint". You can specify a custom key to use like this:
new Session_Security('foo');
If a hijack attempt is detected, the would-be attacker is pushed to a new session. If you wish to take any action in the case of a hijack attempt, you can detect them like this:
$session = new Session_Security;
if ($session->isHijacked()) {
// Do something
}