PHP iterate through an XML file with an invalid structure

Question

How do I iterate through an XML file like shown below? It's output without any root or parent nodes. Some elements repeat, but some don't. And, it's a large file output from a legacy application.

<name>Chair</name>
<price>$53</price>
<quantity>20</quantity>
<units>Piece</units>
<name>Lamp</name>
<price>$20</price>
<quantity>90</quantity>
<units>Piece</units>
<name>Table</name>
<price>$35</price>
<quantity>10</quantity>
<units>Piece</units>
<material>Wood</material>
<name>Pen Holder</name>
<price>$5</price>
<quantity>20</quantity>
<units>Piece</units>
<color>Black</color>

This is how I do it otherwise, but it wont work with this.

$data=simplexml_load_file("inventory.xml");

foreach($data->item as $item) {
        echo "Name: " . $item->name . "<br>";
        echo "Price: " . $item->price . "<br>";
        echo "Quantity: " . $item->quantity . "<br>";
        echo "Units: " . $item->units . "<br>";
        echo "Color: " . $item->color . "<br>";
}

Is there any way you could pre-process it? Like put a root element; put a parent tag; iterate line-by line taking note of the tags you encounter; as soon as you find one you already saw, that means the start of another object, then put closing and opening tags there; once you're out of input close the last parent and close the root. Now you have valid xml. — Federico klez Culloca
– Federico klez Culloca, Commented Jun 18, 2018 at 7:10
Either way you will be stuck with writing your own parser - you'll need it to pre-process the file so you'd be able to use standard XML parser afterwards or you'll just parse and use the data. — Jirka Hrazdil
– Jirka Hrazdil, Commented Jun 18, 2018 at 7:17
you could either fix the system that spews out the invalid xml and turn it into a valid one, or just treat the whole thing as a string and parse it yourself. — Kevin
– Kevin, Commented Jun 18, 2018 at 7:33

Gordon · Accepted Answer · 2018-06-18 08:35:02Z

Adding a root element is easy. You just load the XML into a string and then append and prepend as needed. However, grouping the various elements in items is a bit trickier and largely depends on the XML. The following code will work with the XML you show:

<?php

$xml = 'your xml from the question';

$dom = new DOMDocument;
$dom->loadXml("<root>$xml</root>");

$fixed = new DOMDocument();
$fixed->loadXML("<inventory><items/></inventory>");
$fixed->formatOutput = true;

$items = $fixed->getElementsByTagName('items')->item(0);
foreach ($dom->documentElement->childNodes as $node) {
    if ($node->nodeName === 'name') {
        $item = $fixed->createElement('item');
        $item->appendChild($fixed->createElement($node->nodeName, $node->nodeValue));
        $next = $node->nextSibling;
        while ($next !== null) {
            if ($next instanceof DOMElement) {
                if ($next->nodeName !== 'name') {
                    $item->appendChild($fixed->createElement($next->nodeName, $next->nodeValue));
                } else {
                    $items->appendChild($item);
                    break;
                }
            }
            $next = $next->nextSibling;
        }
    }
}
echo $fixed->saveXML();

This will create two documents:

Your legacy XML with a dummy <root> element so we can process it
A document with the root element <inventory> and an empty element <items>.

We will then iterate all the elements in the legacy XML. When we find a <name> element, we create a new <item> element and add the <name> element as a child. We then check every following sibling to the <name> element. If it's not a <name> element, we will add it to the <item> as well. When it's another <name>, we add the <item> to the <items> collection and start over.

This will then produce:

<?xml version="1.0"?>
<inventory>
  <items>
    <item>
      <name>Chair</name>
      <price>$53</price>
      <quantity>20</quantity>
      <units>Piece</units>
    </item>
    <item>
      <name>Lamp</name>
      <price>$20</price>
      <quantity>90</quantity>
      <units>Piece</units>
    </item>
    <item>
      <name>Table</name>
      <price>$35</price>
      <quantity>10</quantity>
      <units>Piece</units>
      <material>Wood</material>
    </item>
  </items>
</inventory>

You can probably do all of this in a single document. I felt it was easier to understand with two documents.

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