Description:
------------
The following code sample is a 1:1 copy of one of your samples on php.net. It produce an segmentation fault. I was writing on a very similar subject, which also produce an segmentation fault, after some testing i found the page on php.net and also this sample fail. I set the bug type to security because it is spread accross the most current php versions. I have tested 5.6.27 locally, but all other version also affected. Simple test is to use http://phptester.net/ which end in an internal server error.


Test script:
---------------
<?php

class Foo
{
    var $that;

    function __clone()
    {
        $this->that = clone $this->that;
    }

}

$a = new Foo;
$b = new Foo;
$a->that = $b;
$b->that = $a;

$c = clone $a;
echo 'What happened?';
var_dump($c);

Expected result:
----------------
The normally expected result should be a successful created copy of an object.

Actual result:
--------------
Segmentation fault