Wordpress admin login cookies blocked error after moving servers

Question

Background: had a working Wordpress 3.7 site at olddomain.com.

I moved it to newdomain.com successfully, and in the process added this to wp-config:

Answer 1

I created my Multisite install long ago when you needed a plugin for domain mapping. So I had the file '/wp-content/sunrise.php' and in the wp-config define( 'SUNRISE', 'on' ); It's been working just fine until a recent update to WordPress.

I viewed these errors in my debug.log:

Undefined index: HTTP_HOST in ../public_html/wp-content/sunrise.php on line 10
Undefined index: HTTP_HOST in ../public_html/wp-includes/ms-settings.php on line 57

So I deleted the sunrise file and wp-config sunrise definition and added @max4ever/@duck_boy's cookie definitions to the wp-config file:

define('ADMIN_COOKIE_PATH', '/');
define('COOKIE_DOMAIN', '');
define('COOKIEPATH', '');
define('SITECOOKIEPATH', ''); 

That solved the problem. I can now login!! Note: I tried this definition and it worked as well. Taken from Multisite Setup Guide

define( 'COOKIE_DOMAIN', $_SERVER[ 'HTTP_HOST' ] );