PhD dissertations that consist of "publishable articles"?

Philosopher Jim O'Shea (University College Dublin) raises a question I've heard from many others over the years: 

Do philosophy departments with which you are familiar permit PhD dissertations to consist of several independent papers?

And some issues that arise are:

1. Length (i.e. roughly how many articles)

2. Criteria for publishability. Currently PhD examiners have to certify that the thesis they have passed is in part or as a whole publishable.

3. How closely should the articles be interconnected.

Comments from readers--faculty or graduates or current students--with pertinent experience?  Feel free to add links to departmental webpages that describe the rules that apply to the "paper" option for a dissertation.