interdisciplinary Phd programs in philosophy and computer science (AI, ML)? I have a BA in philosophy and I'm working on an MS in computer science specializing in "Interactive Intelligence" (a blend of HCI, AI, ML).  My end goal is a PhD in philosophy but specializing in AI.

A quick Google search hasn't revealed much that fits this.  Would cognitive science be a better fit?  There's Stanford's "Symbolic Systems" major but not much else.  Anyone aware of a program like this?
I suggest that you don't need a "program" but rather a school and a professor who is willing to be flexible and let you take the lead in large part. Maybe a couple of advisors in different fields. I think there are a lot of top institutions that can afford such flexibility and Stanford is likely one of them. But you should probably pursue this individually and in person. 

I'll note that doctoral programs are normally pretty individualized in any case, and often a student needs to take a lead if the topic is not completely within the expertise of the advisor.