在php和站点安全性中设置cookie

Question

I am building a forum and I am not sure about the best practices of setting up a cookie.

Here is the cookie that I build as user registers the site:

       setCookie($name,$ip,time()+300000,"/");

instead of this: time()+300000. I want the cookie last forever, but I am not sure how to do it.

Also, I have a question regarding on security. how do I check that the cookie wasnt tampered or set by a hacker?

Another question, how do I check if the user allows cookies on his browser?

UPDATE:

I put this as soon as login validation is valid: setCookie($name,$ip,time()+60*60*24*365,"/");

UPDATE:

        if(!isset($_COOKIE['$name'])
        {
            $salt="[e-mail]";
            $hash = SHA2(salt + $_POST['pass']);
            setCookie($name,$hash,time()+60*60*24*365*50,"/");
        }

Answer 1

For duration, just use a big enough number instead of 300000.

time() + 60 * 60 * 24 * 366 * 15 gives you 15 years.

To prevent tampering, use a secure hash function (like SHA-2), store a secret salt (a 256-bit random string, for example) on your server, compute hash = SHA2(salt + data) and set a cookie that holds hash.

Now, when you read the cookies, all you have to do is verify that hash has the correct value.