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Bug #55538 Error when unsetting a child of an SimpleXmlElement
Submitted: 2011-08-30 11:21 UTC Modified: 2023-09-10 20:57 UTC
Votes:7
Avg. Score:4.0 ± 0.8
Reproduced:5 of 5 (100.0%)
Same Version:2 (40.0%)
Same OS:3 (60.0%)
From: csnaitsirch at web dot de Assigned:
Status: Verified Package: SimpleXML related
PHP Version: 5.3.8 OS: Windows 7
Private report: No CVE-ID: None
View Developer Edit
 [2011-08-30 11:21 UTC] csnaitsirch at web dot de 
Description:
------------
Hi. I want to remove a child element of an SimpleXmlElement. But that produces a strange error and I think it's a bug.

This is the error message: Warning: main() [function.main]: Node no longer exists in C:\xampp\htdocs\test.php on line 5

It is very easy to reproduce. Pleas look at the test script.

Test script:
---------------
<?php
$xml = "<root><a><aa></aa></a></root>";
$xml = simplexml_load_string($xml);

foreach ($xml as $tag => $child) {
	unset($xml->{$tag});
}

Expected result:
----------------
No errors.

Actual result:
--------------
Warning: main() [function.main]: Node no longer exists in C:\xampp\htdocs\test.php on line 5

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 [2011-08-30 11:26 UTC] csnaitsirch at web dot de 
I forgot to mention, that the node is removed correctly. The only problem is the error message.
 [2012-10-15 10:20 UTC] opensource at prodigy7 dot de 
Can confirm this behaviour. Please fix or tell us, what we do wrong.
 [2012-10-17 19:51 UTC] csnaitsirch at web dot de 
Sorry, but I am not a core developer. I just made a bug report. I do not know what you made wrong. I just see that there is something wrong...
 [2015-05-12 17:28 UTC] cmb@php.net
-Status: Open +Status: Verified
 [2015-05-12 17:28 UTC] cmb@php.net 
I'm not sure, whether this qualifies as bug in PHP. Actually,
during the iteration over a collection, removing or adding
elements can always have undesired side effects.

What's happening in this case is that after the first and only
element is deleted, the next node is requested
(php_sxe_move_forward_iterator[1]). However, this fails, because
the current element had been removed, and so GET_NODE[2] triggers
the warning.

[1] <https://github.com/php/php-src/blob/55d94a453243cafc2292920e9c91bd2bc551f2be/ext/simplexml/simplexml.c#L2462-L2477>
[2] <https://github.com/php/php-src/blob/55d94a453243cafc2292920e9c91bd2bc551f2be/ext/simplexml/simplexml.c#L89-L96>
 [2015-05-12 21:35 UTC] csnaitsirch at web dot de 
Maybe one could just remove the line 'php_error_docref(NULL, E_WARNING, "Node no longer exists");', because it is just working fine. Or is there a further purpose for this warning?

HHVM does not output any warning (see http://3v4l.org/edMDh)
 [2015-10-14 16:07 UTC] paul at muckypuddle dot com 
I think removing the warning is a valid solution here.
 [2023-09-10 20:57 UTC] nielsdos@php.net 
Nowadays this is an exception. I can fix that it throws an exception. However, this might still not give the expected result.
If we consider the following xml:
$xml = "<root><first/><second/><third/></root>";
Then with the fix, only <first/> will be removed. That's because unsetting removes the node from the document, so when the next iteration hits, there's no next node anymore and the iteration will stop.
It's possible to work around that, but I'm not sure what the expected behaviour would actually be.
 
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