George Schlossnagle has this post pointing to this post on Alan Knowles' blog about PHP4's object model.

The crufty but usually sound Alan Knowles seems to have gone completely crazy:

While PHP4's object model may be regarded as a pain, defaulting to cloning objects is actually rather handy in 9 out of 10 situations.

George notes that trying to clone an object by default is not quite the best idea and is unintuitive for most programming out there...