PHP: remove node from xml by attribute

Question

suppose I have an xml like this:

<products>
    <product id="1">
        <name>aaa</name>
        <producturl>aaa</producturl>
        <bigimage>aaa</bigimage>
        <description>aaa</description>
        <price>aaa</price>
        <categoryid1>aaa</categoryid1>
        <instock>aaa</instock>
    </product>
    <product id="2">
        <name>aaa</name>
        <producturl>aaa</producturl>
        <bigimage>aaa</bigimage>
        <description>aaa</description>
        <price>aaa</price>
        <categoryid1>aaa</categoryid1>
        <instock>aaa</instock>
    </product>
</products>

and I need to delete certain node depending on the id attribute, if this attribute is in an array.

I've tried different ways, but the xml is outputted always as the original one!

My code so far:

<?php header("Content-type: text/xml");
$url="http://www.aaa.it/aaa.xml";
$url=file_get_contents($url);
$array=array("1","4","5");
$doc=new SimpleXMLElement($url);
foreach($doc->product as $product){
    if(!in_array($product['id'],$array)){
        $dom=dom_import_simplexml($product);
        $dom->parentNode->removeChild($dom);
        // unset($doc->product->$product);
    }
}
echo $doc->asXml(); ?>

Thanks a lot everyone.

Answer 1

Consider a partly XPath and XSLT solution, both siblings in the Extensible Stylesheet Family. XPath is first used to retrieve all current product ids which is then compared with current array of ids to keep using array_diff. XSLT is then iteratively built to remove nodes according to these unmatched ids. Removing nodes in XSLT requires simply an empty template match.

// Load the XML source
header("Content-type: text/xml");
$url="http://www.aaa.it/aaa.xml";
$url=file_get_contents($url);
$doc=new SimpleXMLElement($url);

// Retrieve all XML product ids with XPath
$xpath = $doc->xpath("//product/@id");
$xmlids = [];
foreach($xpath as $item => $value){ $xmlids[] = (string)$value; }

// Compare difference with $array
$array = array("1","4","5");
$removeids = array_diff($xmlids, $array);

// Dynamically build XSLT string for each resulting id
foreach($removeids as $id){        
  $xslstr='<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
             <xsl:output version="1.0" encoding="UTF-8" indent="yes" />
             <xsl:strip-space elements="*"/>

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

              <xsl:template match="product[@id=\''.$id.'\']"/>

           </xsl:transform>';                    
  $xsl = new SimpleXMLElement($xslstr);

  // Configure the transformer and run
  $proc = new XSLTProcessor;
  $proc->importStyleSheet($xsl);
  $newXML = $proc->transformToXML($doc);

  // Adjust $doc object with each loop
  $doc = new SimpleXMLElement($newXML);
}

// Echo Output    
echo $doc->asXML();