I have a multisite wordpress installation with the domain mapping plugin, running multiple domains on the same wordpress installation. I have recently been trying to get the w3 total cache plugin installed and working, and part of this involves setting up a static subdomain(s) for serving cookieless static content from.
My understanding is that I need to tell wordpress to apply cookies only to the www. subdomains, otherwise it will apply cookies to the static subdomains as well. I have tried using
in wp-config.php (obviously this would need to be set to something like $_SERVER["HTTP_HOST"] or $_SERVER["SERVER_NAME"] in a real use case). But I get an error saying that 'COOKIE_DOMAIN' must not be defined and to remove it from wp-config.php.
I have also checked through the site settings for one of the domains in the Network Admin dashboard, but couldn't see anything to do with cookies.
Can anyone help me with making it so that cookies are set only for www. subdomains?