Dynamically adding methods in PHP

gistfile1.php

<?php

class DynamicMethod
{
    protected $dynamic_methods = array();

    public function __call($name, $args)
    {
        if ($this->dynamic_methods[$name]) {
            return call_user_func_array($this->dynamic_methods[$name], $args);
        }

        super($name, $args);
    }

    public function define_method($name, $method)
    {
        if (!is_callable($method)) throw new RuntimeException();
        $this->dynamic_methods[$name] = $method;
    }
}

$df = new DynamicMethod();

$df->define_method('echo_hoge', function () { echo 'hoge' . PHP_EOL; });
$df->echo_hoge();// hoge

$df->define_method('multi', function ($a, $b) { return $a * $b; });
echo $df->multi(3, 4);// 12