Description:
------------
I want to cache the object returned by simplexml_load_string() or simplexml_load_file().
Fisrt, I seriaize the object and save it into file.
And I read saved string and try to unserialize it.
But PHP not handle it collectly.

Reproduce code:
---------------
<?
    $data = <<<XML
<?xml version='1.0' standalone='yes'?>
<movies>
    <movie>
        <title>PHP: Behind the Parser</title>
    </movie>
</movies>
XML;
    $xml = simplexml_load_string($data);
    $str = serialize($xml);
    echo "$str\n";
    $new_xml = unserialize($str);
    echo serialize($new_xml)."\n";
?>


Expected result:
----------------
O:17:"simplexml_element":1:{s:5:"movie";O:17:"simplexml_element":1:{s:5:"title";s:22:"PHP: Behind the Parser";}}
O:17:"simplexml_element":1:{s:5:"movie";O:17:"simplexml_element":1:{s:5:"title";s:22:"PHP: Behind the Parser";}}


Actual result:
--------------
O:17:"simplexml_element":1:{s:5:"movie";O:17:"simplexml_element":1:{s:5:"title";s:22:"PHP: Behind the Parser";}}
 
Warning: Node no longer exists in /home/gen128/project/mogaha_2004/docs/08_devel/02_research/php-xml/simplexml_performance/test_serialize_xml.php on line 13
 
Warning: Node no longer exists in /home/gen128/project/mogaha_2004/docs/08_devel/02_research/php-xml/simplexml_performance/test_serialize_xml.php on line 13
 
Warning: Node no longer exists in /home/gen128/project/mogaha_2004/docs/08_devel/02_research/php-xml/simplexml_performance/test_serialize_xml.php on line 14
O:17:"simplexml_element":0:{}