Cookie not being reset in PHP - php

Question

I am new to cookies. I created a user login php class that uses a cookie to store a unique MD5 key to remember a user that has logged in. However, the cookie is not being reset when the user logs out. I created a function from code I found on stack overflow to clear the cookies on logout.
static public function clearCookies()
{
$past = time() - 3600;
foreach ( $_COOKIE as $key => $value )
{
$value = '';
setcookie( $key, $value, $past );
setcookie( $key, $value, $past, '/' );
}
}
However, the cookie is still not being cleared.
This is the line of code that sets the cookie
setcookie("auth_key", $authKey, time() + 60 * 60 * 24 * 7);
Thanks ahead of time

Answer 1

Try to add
static public function clearCookies()
{
$past = time() - 3600;
foreach ( $_COOKIE as $key => $value )
{
$value = '';
setcookie( $key, $value, $past );
setcookie( $key, $value, $past, '/' );
unset($_COOKIE[$key]);
}
}
You have to note that changed cookies are readable AFTER sending them to client (if you do not set them manually via $_COOKIE), so the next refresh.

Answer 2

Here is the solution that worked.
I changed
setcookie("auth_key", $authKey, time() + 60 * 60 * 24 * 7);
to
setcookie("auth_key", $authKey, time() + 60 * 60 * 24 * 7, '/');
It seems that the cookie was not being reset because the url it was being reset from was different than the url it was set in. After adding '/' it could be reset from the new url.