PHP Adding method dynamically, meta programming example in PHP 5.3

Meta.php

<?php
/**
 * Example in PHP 5.3 
 */
class Meta
{
    
    private $methods = array();

    public function addMethod($methodName, $methodCallable)
    {
        if (!is_callable($methodCallable)) {
            throw new InvalidArgumentException('Second param must be callable');
        }
        $this->methods[$methodName] = $methodCallable;
    }

    public function __call($methodName, array $args)
    {
        if (isset($this->methods[$methodName])) {
            array_unshift($args, $this);
            return call_user_func_array($this->methods[$methodName], $args);
        }

        throw RunTimeException('There is no method with the given name to call');
    }

}

test.php

<?php
/**
 * Example in PHP 5.3 
 */
require 'Meta.php';

$meta = new Meta();

$meta->addMethod('color', function ($self) {
    $self->name = 'My Name';
    return '#00000';
});

echo $meta->color(), PHP_EOL;
echo $meta->name, PHP_EOL;