XMLReader differentiating nested nodes with same name - php

Question

Trying to work with an external xml file, which is stacked like this:
<?xml version="1.0" encoding="UTF-8"?>
<merchandiser xsi:noNamespaceSchemaLocation="merchandiser.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<header>
<merchantId>44235</merchantId>
<merchantName>Feelunique (UK)</merchantName>
<createdOn>04/27/2020 00:05:33</createdOn>
</header>
<product part_number="99082" manufacturer_name="Sanctuary Spa" sku_number="99082" name="Sanctuary Spa Sleep Dream Easy Pillow Mist 100ml" product_id="15927186808">
<URL>
<product>https://click.linksynergy.com/link?id=y/LyuzvjryY&offerid=687217.15927186808&type=15&murl=https%3A%2F%2Fwww.feelunique.com%2Fp%2FSanctuary-Spa-Sleep-Dream-Easy-Pillow-Mist-100ml%26curr%3DGBP</product>
</URL>
</product>
</merchandiser>
As you can see the node <product> is used twice, and I need to grab an attribute from the first one, and the value in the second.
My code seems to jump straight to the second one by default and allows me to define the $xml->value of the second <product> node, but I can't seem to figure out how to separate the two in my code and get the attribute I need.
while($xml->read()) {
if($xml->nodeType == XMLReader::ELEMENT) {
if($xml->localName == 'header') {
$header = array();
}
if($xml->localName == 'merchantName') {
$xml->read();
$header['merchant'] = addslashes($xml->value);
}
if($xml->localName == 'product') {
$product = array();
$product['merchant'] = $header['merchant'];
$product['title'] = $xml->getAttribute('name');
}
if($xml->localName == 'product') {
$xml->read();
$product['link'] = $xml->value;
}
}
}
Can somebody point me in the right direction as to how I can achieve both values in my php code?

Answer 1

This isn't a complete solution, but just a demonstration of how to reach elements from each of the two product nodes - and you can modify it as needed:
$doc = new DOMDocument();
$doc->loadXML($xml);
$xpath = new DOMXpath($doc);
$product = $xpath->evaluate("//product/#name");
$link = $xpath->evaluate("//product//URL//product");
foreach ($product as $node1) {
foreach ($link as $node2){
echo trim($node2->nodeValue), PHP_EOL,trim($node1->nodeValue);
}}
Output:
https://click.linksynergy.com...
Sanctuary Spa Sleep Dream Easy Pillow Mist 100ml

Answer 2

XMLReader will just jump from node to node, and by the time you hit 'product', both your if statements will evaluated to true.
The only way you can know which product node you are in, is if you retain the information of it's parent.
Doing this with one big loop will be a pain. It's probably better to start a new function after the level-1 product opens and create a new loop to parse the 'product' subtree.
I wrote a library to help with this.
XMLReader (and expat) can be a great tool to parse large XML documents fast, but you need to learn algorithms how to traverse nested structures effectively. If you find that this is too hard to grasp, I would recommend a simpler XML parser like the DOM, or SimpleXML.