<?php
// This is a model
interface HasBalance {
    public function addToBalance(amount);
}

class Customer implements HasBalance {
    public $name;
    public $description;
    ...

    static function getById($id) {
        ...
    }

    public function addToBalance(amount) {
        ...
    }
}

class Company implements HasBalance {
    public function addToBalance(amount) {
        ...
    }
}

// This is a controller
class AccountInformation extends HttpController {
    public function execute(HttpRequest $httpRequest) {
        $info = Customer::getById($httpRequest->query->id);
        $view = View::create('account_information.html', $info);
        return new HttpResponse($view);
    }
}