entry.php

<?php
class Entry {
  private $title;
  private $body;
  private $posted_at;
  private $author;

  public function __set($key, $value) {
    $this->$key = $value;
  }
  
  public function __get($key) {
    return $this->$key;
  }
}

$entry = new Entry();
$entry->title = 'title';
echo $entry->title;