PHP class visibility

gistfile1.php

<?php
class article {
    private $title;

    public function __construct($title) {
        $this->title = $title;
    }

    protected function getTitle() {
        return $this->title;
    }
}

class articleproxy extends article {
    private $article;

    public function __construct(article $article) {
        $this->article = $article;
    }

    public function getTitle() {
        return strtolower($this->article->getTitle());
    }
}

$article = new article('SOME TITLE');
$articleproxy = new articleproxy($article);

print($articleproxy->getTitle());