How to alert a user a minute before his cookie expires in PHP / Javascript?

Question

I am looking for something where I can alert my logged-in users a minute before their cookie expires so that they save the content in the CMS before cookie expiration.. any suggestions on how I can achieve the same?

I have set the following in my auth file

setcookie("USERNAME", $user,time()+9000);
setcookie("AUTHORID", $rec["id"],time()+9000);
setcookie("AUTH", "1",time()+9000);
setcookie("RIGHTS", $rec["rights"],time()+9000);

Answer 1

make additional cookie with time of expiration

setcookie("expiration_time", time,time()+9000);

and after test, time of this cookie

if( $_COOKIES['expiration_time'] + 60 < time() ){
   //... you alert code 
}

Answer 2

How to get cookie expiration date / creation date from javascript?

It's impossible. document.cookie contains information in string like this:

key1=value1;key2=value2;...

So there isn't any information about dates.

You can pass the time expiration to the javascript. One way is to store another cookie, so you have this:

$expireAt = time() + 9000;    
setcookie("USERNAME", $user,$expireAt);
setcookie("AUTHORID", $rec["id"],$expireAt);
setcookie("AUTH", "1",$expireAt);
setcookie("RIGHTS", $rec["rights"],$expireAt);
setcookie("EXPIREAT", $expireAt, $expireAt);

Then, this function to get cookie: ( source )

function getCookie(cname) {
  var name = cname + "=";
  var decodedCookie = decodeURIComponent(document.cookie);
  var ca = decodedCookie.split(';');
  for(var i = 0; i <ca.length; i++) {
    var c = ca[i];
    while (c.charAt(0) == ' ') {
      c = c.substring(1);
    }
    if (c.indexOf(name) == 0) {
      return c.substring(name.length, c.length);
    }
  }
  return "";
}

And set a timer:

let expireat = getCookie("EXPIREAT");
if (expireat) {
  let timeAlert = Number(expireat) - 60;
  setTimeout(function() {
    // Do something
  }, timeAlert);
}

Keep in mind, user can change cookie's values.

Answer 3

You need to that in javascript.

1. server sets fresh expiration time for the cookie
2. javascript with timeout executed
3. on page reload 1,2 again

// save minute before expiration
setTimeout(saveWork, (9000-60)*1000);

function saveWork(){
    // do your stuff
}