PHP 5.3 will include lambda functions and closures.
One interesting thing that will come from this will be the ability to dynamically add a method onto a class at runtime, by combining lambas with the magic __call method..well, at least a hack to make something like this.

Effectively this is similar to traits/grafts, except you don’t have to define anything in a new class, you just extend the object itself when you come to use it.
You could also use a singleton within the Extensible class that keeps track of any added methods and propagates them to any other existing or new instances.

<?php
class Extensible {
        var $_methods=array();
function __call($name, $args) {
                if (array_key_exists($this->_methods, $name)) {
                        call_user_func_array(array($this, $name), $args);
                } else {
                        throw new Exception(‘Unknown dynamic method ‘ . $name . ‘ called in class ‘ . get_class($this));
                }
        }
        function __set($name, $value) {
                if (is_callable($value)) {
                        $this->_methods[$name] = $value;
                }
        }
}
class MyClass extends Extensible {
        function test() {
                echo ‘Non-dynamic method’;
        }
}
$object = new MyClass();
$object->test2 = function () {
        echo ‘Dynamic method’;
};
// test() is defined within the static class definition
$object->test();
// test2() was created dynamically at runtime, but you call it just as
// if it had been in the class definition
$object->test2();
?>

EDIT:
Incidentally this my first proper post sent via email. w00t.