Description:
------------
Segfault occurs in object destructor when a number of conditions appear together.  See code comment for details.

This might be related to bug #36006 (http://bugs.php.net/bug.php?id=36006), but it isn't clear since commenting out *either* of the two lines indicated in the code below avoids the segfault.

Reproduce code:
---------------
<?php

class segfault {
    protected $message = null;
    protected $foo     = null;

    public function __construct ($message) {
        $this->foo = new foo ($this);
        $this->message = $message;
    }

    public function __destruct () {
        // If *either* of the following two lines are omitted, we don't segfault ...
        unset($this->foo);
        print( "MESSAGE: $this->message \n" );
    }
}

class foo {
    protected $ob_ref = null;

    public function __construct ($ob_ref) {
        $this->ob_ref = $ob_ref;
    }
}

$segf = new segfault("ACK");
unset($segf);

?>

Expected result:
----------------
Code prints:
"MESSAGE: ACK"

Actual result:
--------------
No message is printed.  PHP terminates with Segmentation Fault (or Bus error depending on the hardware).