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Bug #55098 SimpleXML iteration produces infinite loop
Submitted: 2011-07-01 04:23 UTC Modified: 2015-09-04 14:46 UTC
Votes:20
Avg. Score:4.4 ± 0.7
Reproduced:18 of 18 (100.0%)
Same Version:9 (50.0%)
Same OS:9 (50.0%)
From: karl dot raab at elements dot at Assigned:
Status: Verified Package: SimpleXML related
PHP Version: 5.3.6 OS: Linux
Private report: No CVE-ID: None
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 [2011-07-01 04:23 UTC] karl dot raab at elements dot at
Description:
------------
see the test script. 

inside the foreach-loop the call of e.g. $nodes->asXml() will reset the iteration 
to the beginning and therefore the loop will forever remain on the second element.

this may be related to bug #50670 and #51846

greets, karl

Test script:
---------------
$xmlString = "<root><a><b>1</b><b>2</b><b>3</b></a></root>";
$xml = simplexml_load_string($xmlString);

$nodes = $xml->a->b;
foreach ($nodes as $nodeData) {
    echo "nodeData: " . $nodeData . "\n";

    //the following code will break the iteration on the second element and resets the pointer
    //happens by any of these methods
    $xml = $nodes->asXml();
    //$nodes->getName();
    //$nodes->attributes();
    //$nodes->children();
    //$nodes->getNamespaces();
    //iteration_breaker($nodes);
}

Expected result:
----------------
nodeData: 1
nodeData: 2
nodeData: 3


Actual result:
--------------
nodeData: 1
nodeData: 2
nodeData: 2
nodeData: 2
nodeData: 2
nodeData: 2
nodeData: 2
nodeData: 2
nodeData: 2
nodeData: 2
and so on...

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 [2011-07-01 05:16 UTC] karl dot raab at elements dot at
already noticed an orphan comment in the test script. 
just ignore the line "//iteration_breaker($nodes);" 

cheers, karl
 [2015-09-04 14:46 UTC] cmb@php.net
-Status: Open +Status: Verified
 [2015-09-04 14:46 UTC] cmb@php.net
Even simpler reproduce script:

    <?php
    $xml = simplexml_load_string('<root><a>1</a><a>2</a></root>');
    $as = $xml->a;
    foreach ($as as $a) {
        var_dump($as);
    }
    ?>

Generally, when iterating over SimpleXMLElement, you must not
access this object inside the loop. That may may work in some
cases, but usually accessing a SimpleXMLElement calls
php_sxe_get_first_node()[1], which calls php_sxe_reset_iterator()[2],
when the element is currently iterated over. Obviously, this leads
to an infinite loop.

[1] <http://lxr.php.net/xref/PHP_5_6/ext/simplexml/simplexml.c#php_sxe_get_first_node>
[2] <http://lxr.php.net/xref/PHP_5_6/ext/simplexml/simplexml.c#php_sxe_reset_iterator>
 
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