Accessing a different's instance protected members in PHP

gistfile1.txt

<?php

abstract class A {
	abstract protected function test();
}

class Api extends A {
	protected function test() { echo 'aaa ', __CLASS__, PHP_EOL; }
}

class Cache extends A {
	
	private $api;
	
	public function __construct(A $api)
	{
		$this->api = $api;
	}
	
	protected function test() { echo 'bbb ', __CLASS__, PHP_EOL; }
	
	public function foo()
	{
		$this->api->test();
	}
	
	public function bar()
	{
		$this->test();
	}
}

$cache = new Cache(new Api());
$cache->foo(); // aaa Api
$cache->bar(); // bbb Cache