There is a discussion going on in php land about introducing closures and lambda functions, there was even a discussion on haskell-cafe about it (chx strikes again ;). About time, I would say. Having this functionality is a bonus. Having it implemented badly or half-arsed is going to do more damage than help. This is a short summary of what do I understand from the rfc and what do I think about it.
// fixed-point combinator
function Y(Lambda &$le) {
return lambda(get_defined_vars(), 'Lambda $f', '
return $f->call($f);
')->call(lambda(get_defined_vars(), 'Lambda $f', '
return $le->call(lambda(get_defined_vars(), \'$x\', \'
return $f->call($f)->call($x);
\'));
'));
}