insert child to XML that is saved as a String - php

Question

I'm working in PHP, I have a large XML saved in a String,I want to insert as a first child a node, I know the name of the parent, is something like:
<mytag Someattributte="anything">
here I want to put my tag
...
a lot of tags
...
</mytag>
How can I do that?

Answer 1

With DOM you use Xpath to fetch nodes, DOM document methods to create new nodes (DOMDocument::createDocumentFragment()) and DOM node methods to insert/append them (DOMDocument::insertBefore()).
Document fragments are a construct that allows you to treat a list of nodes as a single node. And they can load an XML fragment string.
$targetXml = <<<'XML'
<mytag Someattribute="anything">
here I want to put my tag
...
a lot of tags
...
</mytag>
XML;
$fragmentXml = <<<'XML'
<othertag>with text</othertag>
XML;
$document = new DOMDocument();
$document->loadXml($targetXml);
$xpath = new DOMXpath($document);
// fetch the first mytag node that has a Someattribute
foreach ($xpath->evaluate('//mytag[#Someattribute][1]') as $targetNode) {
// create a new fragment
$fragment = $document->createDocumentFragment();
// append the stored xml string to the fragment node
$fragment->appendXml($fragmentXml);
// insert the fragment before the first child of the target node
$targetNode->insertBefore($fragment, $targetNode->firstChild);
}
echo $document->saveXml();
Output:
<?xml version="1.0"?>
<mytag Someattribute="anything"><othertag>with text</othertag>
here I want to put my tag
...
a lot of tags
...
</mytag>
If you XML string is a whole document you need to load it as a separate document instance and import the document element.
foreach ($xpath->evaluate('//mytag[#Someattribute][1]') as $targetNode) {
$import = new DOMDocument();
$import->loadXml($fragmentXml);
$targetNode->insertBefore(
$document->importNode($import->documentElement, TRUE),
$targetNode->firstChild
);
}