Description:
------------
When an object contains an array of other objects 
as a private member variable, if the array is 
returned through a member method, instead of a 
copy a reference to the private array is returned. 
Through this reference the member variable can be
modified outside of the object's scope. Thus, violating the private member variable state.

Reproduce code:
---------------
class Atom {
  private $x = 0;  
  public function __construct($x) {$this->x = $x;}
  public function setX($x)        {$this->x = $x;} 
}
class Element {
  private $atoms = array();  
  public function __construct($NMAX) {
    for ($i=0; $i<$NMAX; ++$i) 
      $this->atoms[] = new Atom($i);
  }
  public function setAtoms($atoms) {$this->atoms = $atoms;}
  public function getAtoms()       {return $this->atoms;} 
}
$element = new Element(3); 
$v = $element->getAtoms(); print_r($v); 
$v[0]->setX(79);           print_r($v);
$w = $element->getAtoms(); print_r($w);

Expected result:
----------------
Array
(
    [0] => Atom Object
        (
            [x:private] => 0
        )

    [1] => Atom Object
        (
            [x:private] => 1
        )

    [2] => Atom Object
        (
            [x:private] => 2
        )

)
Array
(
    [0] => Atom Object
        (
            [x:private] => 79
        )

    [1] => Atom Object
        (
            [x:private] => 1
        )

    [2] => Atom Object
        (
            [x:private] => 2
        )

)
Array
(
    [0] => Atom Object
        (
            [x:private] => 0
        )

    [1] => Atom Object
        (
            [x:private] => 1
        )

    [2] => Atom Object
        (
            [x:private] => 2
        )

)


Actual result:
--------------
Array
(
    [0] => Atom Object
        (
            [x:private] => 0
        )

    [1] => Atom Object
        (
            [x:private] => 1
        )

    [2] => Atom Object
        (
            [x:private] => 2
        )

)
Array
(
    [0] => Atom Object
        (
            [x:private] => 79
        )

    [1] => Atom Object
        (
            [x:private] => 1
        )

    [2] => Atom Object
        (
            [x:private] => 2
        )

)
Array
(
    [0] => Atom Object
        (
            [x:private] => 79
        )

    [1] => Atom Object
        (
            [x:private] => 1
        )

    [2] => Atom Object
        (
            [x:private] => 2
        )

)