Finding Cookie Expiry Time in PHP?

Question

I want to see my cookie expiry time.

My Code is like this :

setcookie('blockipCaptcha','yes',time() + (86400 * 7));

But I want to see the cookie expiry time whenever I am refreshing the page. How do to this?

Answer 1

You cannot get the cookie expiry time unless you encode that information as part of the cookie (the browser, who has this information, does not send it over). For example:

$expiresOn = time() + (86400 * 7);
setcookie('blockipCaptcha','yes;expires=' . $expiresOn, $expiresOn);

Even then, someone could theoretically tamper with the cookie contents so you cannot really "trust" the value unless the cookie contents are also cryptographically authenticated with a HMAC.

An example of how to sign and authenticate the contents of the cookie:

$secretKey = ''; // this must be a per-user secret key stored in your database
$expiresOn = time() + (86400 * 7);
$contents = 'yes;expires=' . $expiresOn;
$contents = $contents . ';hmac='. hash_hmac('sha256', $contents, $secretKey);

When you get back the contents of the cookie, strip out and validate the HMAC part:

$contents = $_COOKIE['blockipCaptcha'];

// I 'm doing this slightly hacky for convenience
list ($contents, $hmac) = explode(';hmac=', $contents);

if ($hmac !== hash_hmac('sha256', $contents, $secretKey)) {
    die('Someone tampered with the contents of the cookie!');
}