New observer pattern (test 1)

new-observer.php

<?php

interface imethods
{
    public function add($x, $y);
    public function sub($x, $y);
}

class methods
{
    protected function _add($args)
    {
        list($num1, $num2) = $args;

        $answer = ($num1 + $num2);
        echo $num1.' + '.$num2.' = '.$answer;
        return $answer;
    }
    protected function _sub($args)
    {
        list($num1, $num2) = $args;

        $answer = ($num1 - $num2);
        echo $num1.' - '.$num2.' = '.$answer;
        return $answer;
    }
}

final class Calculator extends methods implements imethods
{
    public function add($x, $y)
    {
        return $this->__call(__FUNCTION__, func_get_args());
    }
    public function sub($x, $y)
    {
        return $this->__call(__FUNCTION__, func_get_args());
    }

    public function __call($method, $args)
    {
        self::log($method, $args, $this->{'_'.$method}($args));
    }

    static private function log($method, $args, $return = false)
    {
        $data = array
        (
            'method' => $method,
            'args'   => $args,
            'return' => $return
        );
        // log function here
        var_dump($data);
    }
}

$enter = new Calculator();
$enter->add(10, 20);
$enter->sub(15, 40);