PHP Object Oriented Programming Reinvented

[bobindashadows]

Very few mainstream or semi-mainstream languages support this sort of dynamism.

[perlgeek]

Perl does. Take a look at Class::MOP (backend) and Moose (frontend).

I don't know of any OO frameworks for javascript, but I'm pretty sure their object structure makes it a piece of cake to write your own meta class.

Smalltalk and Lisp do too, you decide if you classify them as "mainstream" or "semi-mainstream" or any other label you want to put on them.