Remove a node from XML with namespace and generate new XML

Question

I am trying to filter the results of an XML feed generated for Facebook. Currently, the feed looks like this

<?xml version="1.0" encoding="UTF-8"?>
<rss xmlns:g="http://base.google.com/ns/1.0" version="2.0">
  <channel>
    <title><![CDATA[Title]]></title>
    <link><![CDATA[https:/path/]]></link>
    <description>WooCommerce Product List RSS feed</description>
    <metadata>
      <ref_application_id>451257172939091</ref_application_id>
    </metadata>
    <item>
      <g:id>anID</g:id>
      <g:inventory>5</g:inventory>
      <g:description><![CDATA[Some Text]]></g:description>
      <g:condition>new</g:condition>
      <g:mpn>sku</g:mpn>
      <g:title>Product Title</g:title>
      <g:availability>in stock</g:availability>
      <g:price>185.00 EUR</g:price>
      <g:brand><![CDATA[BRAND1]]></g:brand>
    </item>
    <item>
      <g:id>anID</g:id>
      <g:inventory>5</g:inventory>
      <g:description><![CDATA[Some Text]]></g:description>
      <g:condition>new</g:condition>
      <g:mpn>sku</g:mpn>
      <g:title>Product Title</g:title>
      <g:availability>in stock</g:availability>
      <g:price>185.00 EUR</g:price>
      <g:brand><![CDATA[BRAND2]]></g:brand>
    </item>
    <item>
      <g:id>anID</g:id>
      <g:inventory>5</g:inventory>
      <g:description><![CDATA[Some Text]]></g:description>
      <g:condition>new</g:condition>
      <g:mpn>sku</g:mpn>
      <g:title>Product Title</g:title>
      <g:availability>in stock</g:availability>
      <g:price>185.00 EUR</g:price>
      <g:brand><![CDATA[BRAND2]]></g:brand>
    </item>
............

I need to remove some nodes based on the brand value. My code currently looks like this:

$xmlstr = get_xml_from_url('urlToXMLFeed/xml/testfeed1.xml');
$xmlobj = new SimpleXMLElement($xmlstr);
$xmlobj->registerXPathNamespace("g", "http://base.google.com/ns/1.0");
$i = 0;

foreach($xmlobj->channel->item as $item)
{
    $namespaces = $item->getNameSpaces(true);
    // echo $namespaces;
    $gbrand = $item->children($namespaces['g']);
    $finalBrand = $gbrand->brand;
    if(strcmp($finalBrand,"BRAND2") == 0)
    {
        
        unset($item);
    }
    $i ++;
}

//Format XML to save indented tree rather than one line and save
$dom = new DOMDocument('1.0');
$dom->preserveWhiteSpace = false;
$dom->formatOutput = true;
$dom->loadXML($xmlobj->asXML());
$dom->save('fileName.xml');

The newly generated XML still has the nodes with the BRAND2. Also, tried using this to remove the node

unset($xmlobj->channel->item->{$i});

But the second approach only removes the first occurrence of BRAND2.

Also tried the following:

$domElemsToRemove = array();
.......
    if(strcmp($finalBrand,"BRAND2") == 0)
    {
        $domElemsToRemove[] = $item;
    }
}
....
foreach( $domElemsToRemove as $domElement ){
    $xmlobj->channel->removeChild($domElement);
}

But still the same result

It is much better and easier to use XSLT transformation for such tasks. — Yitzhak Khabinsky, Aug 11 '21 at 14:34

score 1 · Answer 1 · answered Aug 11 '21 at 14:47

1

I found a possible solution for my case. According to a PHP comment here, we can not directly remove nodes, as it was my first approach because it will break the loop. Thus, we have to create a queue with the nodes we wish to remove. Then, based on the answer here the solution is this

foreach( $domElemsToRemove as $domElement )
{
    $dom = dom_import_simplexml($domElement);
    $dom->parentNode->removeChild($dom);
}

That removes all the nodes from the XML object properly!

answered Aug 11 '21 at 14:47

Argiris

189
2
15

Please don't miss the XSLT based solution. – Yitzhak Khabinsky Aug 11 '21 at 14:52
@YitzhakKhabinsky I will definitely try that later on. It's something new to me! But, thank you very much for your response! – Argiris Aug 11 '21 at 14:59
This single line `` does the whole magic. – Yitzhak Khabinsky Aug 11 '21 at 15:12

hakre · Answer 2 · 2021-08-12T19:02:24.790

You're already pretty close. With PHP SimpleXML:

$xmlobj = new SimpleXMLElement($xmlstr);

foreach ($xmlobj->xpath('//item[g:brand="BRAND2"]') as $item) {
    unset($item[0]);
}

# output ...

See it running online: https://3v4l.org/nWOrY

This works already because:

unset($item) only unsets the variable. Using the SimpleXMLElement self-reference $item[0] removes the element from the XML document with unset.
Traversal by foreach ($xmlobj->channel->item as $item) invalidates if unset($item[0]) is called within the foreach-body (PHP Fatal error: Uncaught Error: SimpleXMLElement is not properly initialized). Foreach-ing over an array of SimpleXMLElements is immune. $xmlobj->xpath() returns such an array already.

Such an array could be created as well with iterator_to_array($xmlobj->channel->item, false) (second parameter false with SimpleXML!) if you do not want to use SimpleXMLElement::xpath() function.
XPath in SimpleXML has the XPath Namespaces already registered ("g" for "http://base.google.com/ns/1.0" as it is defined in the XML document element).
XPath itself is powerful in querying the document for elements (or attributes).

Some references:

Compare with the answer Remove a child with a specific attribute, in SimpleXML for PHP (2008 by Stefan Gehrig) which is nearly identical to your scenario, different only in the decision on attribute - not element - content and don't miss the "By the way: selecting specific nodes is much more simple when you use XPath" part at the end.

Then compare with my 2013 answer there that shows the SimpleXMLElement self-reference (with unset). It is a concept that dates back to earlier contributions on Stackoverflow, for example in Remove multiple empty nodes with SimpleXML (2012 by Beshoy Girgis) and there should be a couple more.

Perhaps Kamil Szot coined the term SimpleXMLElement self-reference back in June 2010 with How can I set text value of SimpleXmlElement without using its parent?

And some closing comment:

I write this as well because as far as SimpleXML is of concern, DOMNodeList or importing into DOM (dom_import_simplexml()) should not be necessary for element deletion. It's more about using an array if you want to delete a list of elements as the traversal (perhaps similar to DOMNodeList behaviour) as just foreach-ing breaks with the first deletion.

score 0 · Answer 3 · answered Aug 11 '21 at 14:45

Here is a solution based on XSLT.

It removes all <item> elements with the g:brand='BRAND2'.

Input XML

<?xml version="1.0" encoding="UTF-8"?>
<rss xmlns:g="http://base.google.com/ns/1.0" version="2.0">
    <channel>
        <title><![CDATA[Title]]></title>
        <link><![CDATA[https:/path/]]></link>
        <description>WooCommerce Product List RSS feed</description>
        <metadata>
            <ref_application_id>451257172939091</ref_application_id>
        </metadata>
        <item>
            <g:id>anID</g:id>
            <g:inventory>5</g:inventory>
            <g:description><![CDATA[Some Text]]></g:description>
            <g:condition>new</g:condition>
            <g:mpn>sku</g:mpn>
            <g:title>Product Title</g:title>
            <g:availability>in stock</g:availability>
            <g:price>185.00 EUR</g:price>
            <g:brand><![CDATA[BRAND1]]></g:brand>
        </item>
        <item>
            <g:id>anID</g:id>
            <g:inventory>5</g:inventory>
            <g:description><![CDATA[Some Text]]></g:description>
            <g:condition>new</g:condition>
            <g:mpn>sku</g:mpn>
            <g:title>Product Title</g:title>
            <g:availability>in stock</g:availability>
            <g:price>185.00 EUR</g:price>
            <g:brand><![CDATA[BRAND2]]></g:brand>
        </item>
        <item>
            <g:id>anID</g:id>
            <g:inventory>5</g:inventory>
            <g:description><![CDATA[Some Text]]></g:description>
            <g:condition>new</g:condition>
            <g:mpn>sku</g:mpn>
            <g:title>Product Title</g:title>
            <g:availability>in stock</g:availability>
            <g:price>185.00 EUR</g:price>
            <g:brand><![CDATA[BRAND2]]></g:brand>
        </item>
    </channel>
</rss>

XSLT

<?xml version='1.0'?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:g="http://base.google.com/ns/1.0">
    <xsl:output method="xml" indent="yes" cdata-section-elements="title link g:description g:brand" encoding="utf-8" omit-xml-declaration="no"/>
    <xsl:strip-space elements="*"/>

    <xsl:template match="@*|node()">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()"/>
        </xsl:copy>
    </xsl:template>

    <xsl:template match="item[g:brand='BRAND2']"/>
</xsl:stylesheet>

Output XML

<?xml version='1.0' encoding='utf-8' ?>
<rss xmlns:g="http://base.google.com/ns/1.0" version="2.0">
  <channel>
    <title><![CDATA[Title]]></title>
    <link><![CDATA[https:/path/]]></link>
    <description>WooCommerce Product List RSS feed</description>
    <metadata>
      <ref_application_id>451257172939091</ref_application_id>
    </metadata>
    <item>
      <g:id>anID</g:id>
      <g:inventory>5</g:inventory>
      <g:description><![CDATA[Some Text]]></g:description>
      <g:condition>new</g:condition>
      <g:mpn>sku</g:mpn>
      <g:title>Product Title</g:title>
      <g:availability>in stock</g:availability>
      <g:price>185.00 EUR</g:price>
      <g:brand><![CDATA[BRAND1]]></g:brand>
    </item>
  </channel>
</rss>

Remove a node from XML with namespace and generate new XML

3 Answers3