Access to protected base class members of a subclass via another subclass.

gistfile1.php

<?php

class Base
{
  private $x;

  public function getX()
  {
    return $this->x;
  }

  public function setX($x)
  {
    $this->x = $x;
  }
}

/**
* This class tries to ensure that $x is always an integer.
*/
class GoodChild extends Base
{
  public function setX($x)
  {
    if (is_integer($x))
    {
      parent::setX(x);
    }
  }
}

/**
* This class circumvents GoodChild's security system.
*/
class EvilChild extends Base
{
  public function setX(Base $b, $x)
  {
    $b->setX($x);
  }
}

$good = new GoodChild();
$evil = new EvilChild();
$evil->setX($good, 'foo'); // Works not!