Description:
------------
I make one object instance. Then, pass it to another object. Then, change original instance. Now I have two different objects.

Reproduce code:
---------------
<?php
class classA {
    public $id = "";
    public function __construct($id) {
        $this->id = $id;
    }
}
class classB {
    public $reference = null;
    public function __construct($ref) {
        $this->reference = $ref;
    }
}
$a = new classA("object 1");
$test = new classB($a);
$a = new classA("object 2");
echo $a->id, "<br>", $test->reference->id;
?>

Expected result:
----------------
object 2
object 2

Actual result:
--------------
object 2
object 1

However, adding references solves the problem:

class classB {
    public $reference = null;
    public function __construct(&$ref) {
        $this->reference =& $ref;
    }
}

This works as expected.

So, the question is are objects being passed by reference or what?