オブジェクトに動的にメソッドを追加するトレイト

<?php

trait MethodAttachable
{
    protected $_callbacks = array();

    public function __set($name, $value)
    {
        if (is_callable($value)) {
            $this->_callbacks[$name] = $value;
        }

        $this->{$name} = $value;
    }

    public function magicCallMethodAttachable($method, $args)
    {
        if (isset($this->_callbacks[$method])) {
            $callback = $this->_callbacks[$method];
            if ($callback instanceof \Closure) {
                $callback = \Closure::bind($callback, $this, get_class($this));
            }

            return call_user_func_array($callback, $args);
        }

        throw new \BadMethodCallException(sprintf('Call to undefined method %s::%s', get_class($this), $method));
    }

    public function __call($method, $args)
    {
        return $this->magicCallMethodAttachable($method, $args);
    }
}

使い方:

<?php

class Foo
{
    use MethodAttachable;
}

$foo = new Foo();
$foo->name = 'wozozo';
$foo->eat = function($food) {
    echo sprintf('%s eats %s.', $this->name, $food), PHP_EOL;
};

$foo->eat('cocoiti');