The example using Javascript

var now = new Date();
var timestamp = now.getTime();
 
var cookie = document.cookie;
var index = cookie.indexOf ("user_id");
 
if (index == -1) {
    document.write ("It looks like you have not been here before.<br>");
    var userid = "user" + timestamp;
    document.write ("From now on I will call you " + userid + ".<br>");
    document.cookie = "user_id=" + userid;
} else {
    document.write ("Hey, I know you!<br>");
    document.write ("You sent me a cookie containing:<br>");
    document.write (cookie);
}