The problem is that the URL it’s checking for accessibility may not be valid, and in my case, isn’t. That is, in my environment, https://cas-host/cas/context returns a 404, but https://cas-host/cas/context/login returns a 200.
The phpCAS client silently tacks ‘login’ (or ‘logout’) onto the “server base url” before redirecting the user to CAS.
