Indirect modification of overloaded property Hoge::$hage has no effect in ...

sample.php

<?php
class Hoge {
  private $data = array();
  public function __get($key) {
    return array_key_exists($key, $this->data) ? $this->data[$key] : null;
  }
  public function __set($key, $value) {
    return $this->data[$key] = $value;
  }
}
$hoge = new Hoge();
$hoge->hage = array(1);
$hoge->hage[0] = 2;