Edit XML file (remove node and add new one) - php

Question

I have problems to deal with XML in PHP. What i want is to remove a not needed element and replace it with a other one.
Let's say the XML looks like this:
<?xml version="1.0" encoding="UTF-8"?>
<software>
<info>
<version>1.2</version>
<lasterror>1386680712</lasterror>
</info>
<decryption>
<funcgroup siglength="86">
<func>
<name>Mk</name>
<args>$a</args>
<code>XXXX</code>
</func>
<func>
<name>Nk</name>
<args>$a,$b</args>
<code>XXXX</code>
</func>
</funcgroup>
</decryption>
</software>
PHP Code:
$domtree = new DOMDocument('1.0', 'UTF-8');
$domtree->loadXML(file_get_contents('test.xml'));
$thedocument = $domtree->documentElement;
$list = $thedocument->getElementsByTagName('funcgroup');
foreach ($list as $domElement) {
$sig_length = $domElement->getAttribute('siglength');
if($sig_length == $signature_length) {
$domElement->parentNode->removeChild($domElement);
break;
}
}
$some_stuff = $domtree->getElementsByTagName('software');
$some_stuff = $domtree->getElementsByTagName('decryption');
$funcgroup = $domtree->appendChild($domtree->createElement('funcgroup'));
$funcgroup->setAttribute('siglength', $signature_length);
$func = $funcgroup->appendChild($domtree->createElement('func'));
$func->appendChild($domtree->createElement('name', $outer_element[0]));
$func->appendChild($domtree->createElement('args', $outer_element[1]));
$code = $func->appendChild($domtree->createElement('code'));
$code->appendChild($domtree->createTextNode($outer_element[2]));
Note: I removed some stuff otherwise it would get too complicated i guess. The above code shows what i do, but without some other loops and variables which are not needed in that question. Every variable (and array) is defined. So don't worry about that.
What i want is to remove the whole <funcgroup siglength="86"> in order to replace it with a different one.
The script works fine, but there is one problem in the output XML. It looks like this:
<?xml version="1.0" encoding="UTF-8"?>
<software>
<info>
<version>6.3</version>
<lasterror>1386680712</lasterror>
</info>
<decryption/>
</software>
<funcgroup siglength="86">
<func>
<name>Nk</name>
<args>$a</args>
<code>YYYYY</code>
</func>
<func>
<name>Ok</name>
<args>$a,$b</args>
<code>YYYY</code>
</func>
</funcgroup>
As you can see, the closing software and decryption tags are on the wrong place now.
How can i fix that? I spent hours but can't find a working solution.
The problem is caused by the removeChild() since it works fine if i do not remove something.

Answer 1

You are adding your new child node to the document itself (instead of the decryption node), which is not what you want
$domtree->appendChild
Instead you should:
$decryption = $domtree->getElementsByTagName('decryption')->item(0);
$funcgroup = $decryption->appendChild($domtree->createElement('funcgroup'));
Edit:
You can edit the text value of the lasterror node by doin:
$domtree->getElementsByTagName('lasterror')->item(0)->firstChild->nodeValue = "New value";
Consult the documentation of the DOMNodeList and DOMNode class to see what else you can do with it.