PHP Bug #62189

<?php

class Widget implements Serializable
{
    public $references = array();
    public $config;

    public function serialize()
    {
        $vars = get_object_vars($this);

        $vars['config'] = serialize($vars['config']);

        $serialized = serialize($vars);

        return $serialized;
    }

    public function unserialize($serialized)
    {
        $array = unserialize($serialized);

        $array['config'] = unserialize($array['config']);

        foreach($array as $k => $v)
        {
            $this->$k = $v;
        }
    }
}

class Placeholder
{
    public $id;

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

$collection = array();

$placeholder1 = new Placeholder(1);
$placeholder2 = new Placeholder(2);

$widget1 = new Widget;
$widget1->config = array('id_section' => 9);
$widget1->references[] = $placeholder1;

$widget2 = new Widget;
$widget2->config = array('id_section' => 9);
$widget2->references[] = $placeholder2;

$widget3 = new Widget;
$widget3->config = array('id_section' => 9);
$widget3->references[] = $placeholder1;

$widget4 = new Widget;
$widget4->config = array('id_section' => 9);
$widget4->references[] = $placeholder1;

$collection[] = $widget1;
$collection[] = $widget2;
$collection[] = $widget3; // reference to placeholder will be missing here
$collection[] = $widget4; // reference to placeholder will be missing here

print_r(unserialize(serialize($collection)));