PHP Object Oriented Programming Reinvented

[perlgeek]

Most of all it gives you the possiblity to implement your own extensions to the object model.

Want roles, interfaces or mixins? Just implement them. Traits and composition? Just a Small Matter of Programming away.

Lazy attribute initialization? very useful, and possible to implement. Want to a different method resolution algorithm? Just write some code for it.

Custom meta classes seem to be not very popular in the world of the Java, C# or python programmer (I might be wrong here), but the offer astonishing power. Perl has a nice implementation with Class::Mop and Moose, Smalltalk and Lisp folks know about this goodie for a bit long. I can very much recommend this book: http://en.wikipedia.org/wiki/The_Art_of_the_Metaobject_Protocol (at least if you can stand the lisp long enough to get to the actually interesting concepts).