Cookies are not removing on Log Out - php

Question

I've got a problem, user can't Log Out because the $_COOKIE's are not actually deleting. I can't find out what could be the problem.
This code is used only once at Log In:
// Log In
$_SESSION['user_id'] = $row['user_id'];
$_SESSION['username'] = $row['username'];
setcookie('user_id', $row['user_id'], time() + 2592000);
setcookie('username', $row['username'], time() + 2592000);
The code below is checking if cookies are set up to make users to be logged in when they relaunch their browser (the "keep me logged in" effect).
// Starting Session
session_start();
// If the session vars aren't set, try to set them with cookies
if (!isset($_SESSION['user_id'])) {
// This check always equals true because cookies are not deleting on Log Out
if (isset($_COOKIE['user_id']) && isset($_COOKIE['username'])) {
$_SESSION['user_id'] = $_COOKIE['user_id'];
$_SESSION['username'] = $_COOKIE['username'];
}
}
This code is launched only once on Log Out:
// Log Out
session_start();
if (isset($_SESSION['user_id'])) {
$_SESSION = array();
if (isset($_COOKIE[session_name()])) {
setcookie(session_name(), '', time() - 2592000, '/');
}
session_destroy();
}
setcookie('user_id', '', time() - 2592000);
setcookie('username', '', time() - 2592000);

Answer 1

Don't use relative times for cookies. if you want to expire a cookie, then use Jan 1 1970 00:00:00. You're assuming that the user's clock is accurate and within an hour of your server's. Given how many people have their VCRs blinking 12:00, this is a bad assumptiong.
As well, why are you storing login information in a client-side cookie? The only cookie you should really be setting is the session cookie, which session_start() already does for you, then store all that information in $_SESSION only.

Answer 2

I think you're doing it way too complicated.
My example where it's just an admin login:
login.php
#session_start();
if (isset($_GET['login'])) {
if($_GET['name'] == $s['admin']){
if($_GET['pw'] == $s['adminpw']){
$_SESSION['isadmin'] = true;
}
}
}
logout.php
#session_start();
unset ($_SESSION['isadmin']);
use session_set_cookie_params() to set the lifetimes

Answer 3

I found why cookies were not removing!
To make sure your cookies will remove, set the same path on removing cookies as on setting them.
// Setting Cookie
setcookie(session_name(), '', time()-2592000, '/'); // The path here is "/"
// Removing Cookie
setcookie(session_name(), '', time()+2592000, '/'); // The path here is "/"