Apparantly there is a scheme in some universities in some of European countries
by which students are allowed to submit a few published journal articles
to a committee in the university and get PhD. articles are considered as a replacement for dissertation. It means if you have a few articles, which are all top peer-reviewed articles mainly on the same topic published in good journals, you can submit them to a committee in the university and they referee them
and grant you a phd. this is i guess mainly for people who are already associated with the university in a way, and again mainly in humanities. Azam says that this scheme is well-established in some countries like Denmark but it doesn't have so many fans because publishing in top journals is time-intensive and not so easy.