protected-member.php

<?php
class Hoge
{
	protected $_val;

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

	public function say()
	{
		echo "say $this->_val\n";
	}
}

class HogeSub extends Hoge
{
	public static function setVal(Hoge $hoge, $val)
	{
		$hoge->_val = $val;
	}
}

class HogeProtect extends Hoge
{
	private $_obj;
	
	public function __construct($obj)
	{
		$this->_obj = $obj;
	}
	
	public function __get($name)
	{
		return $this->_obj->$name;
	}
	
	public function __set($name, $val)
	{
		$this->_obj->$name = $val;
	}
}

///

$hoge = new Hoge(1);

// say 1
$hoge->say();

HogeSub::setVal($hoge, 2);

// say 2
$hoge->say();

$hogeProtect = new HogeProtect($hoge);
$hogeProtect->_val = 3;

// say 3
$hoge->say();