Using PHP SimpleXML to access non-default namespace element attributes

Jesse
February 9, 2023
121 views
3 votes
3 Answers

I have some annoying XML from an API response that looks like:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?><report><QueryResult>
  <ResumptionToken>123456</ResumptionToken>
  <IsFinished>true</IsFinished>
  <ResultXml>
    <rowset xmlns="urn:schemas-microsoft-com:xml-analysis:rowset">
      <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:saw-sql="urn:saw-sql" targetNamespace="urn:schemas-microsoft-com:xml-analysis:rowset">
        <xsd:complexType name="Row">
          <xsd:sequence>
            <xsd:element maxOccurs="1" minOccurs="1" name="Column0" saw-sql:aggregationRule="none" saw-sql:aggregationType="nonAgg" saw-sql:columnHeading="0" saw-sql:displayFormula="0" saw-sql:length="4" saw-sql:precision="12" saw-sql:scale="0" saw-sql:tableHeading="" saw-sql:type="integer" type="xsd:int"/>
            <xsd:element maxOccurs="1" minOccurs="0" name="Column1" saw-sql:aggregationRule="none" saw-sql:aggregationType="nonAgg" saw-sql:columnHeading="ISBN" saw-sql:displayFormula=""Bibliographic Details"."ISBN"" saw-sql:length="255" saw-sql:precision="255" saw-sql:scale="0" saw-sql:tableHeading="Bibliographic Details" saw-sql:type="varchar" type="xsd:string"/>
            <xsd:element maxOccurs="1" minOccurs="0" name="Column2" saw-sql:aggregationRule="none" saw-sql:aggregationType="nonAgg" saw-sql:columnHeading="ISSN" saw-sql:displayFormula=""Bibliographic Details"."ISSN"" saw-sql:length="255" saw-sql:precision="255" saw-sql:scale="0" saw-sql:tableHeading="Bibliographic Details" saw-sql:type="varchar" type="xsd:string"/>
            <xsd:element maxOccurs="1" minOccurs="0" name="Column3" saw-sql:aggregationRule="none" saw-sql:aggregationType="nonAgg" saw-sql:columnHeading="Publication Date" saw-sql:displayFormula=""Bibliographic Details"."Publication Date"" saw-sql:length="255" saw-sql:precision="255" saw-sql:scale="0" saw-sql:tableHeading="Bibliographic Details" saw-sql:type="varchar" type="xsd:string"/>
          </xsd:sequence>
        </xsd:complexType>
      </xsd:schema>
      <Row>
        <Column0>0</Column0>
        <Column1>55555555 444444445</Column1>
        <Column3>[2019]</Column3>

      </Row>
      <Row>
        <Column0>0</Column0>
        <Column1>555555555</Column1>
        <Column3>©2009.</Column3>
      </Row>

I’m using PHP’s SimpleXML to parse this data, but am struggling to access the column headers located in the non-default namespace under xsd:element. For example, I need to access the value: saw-sql:columnHeading="Publication Date", as this column can be dynamic and isn’t always "Publication Date". So I’m looking to pluck out the values for saw-sql[@columnHeading].

I’ve tried all manners of registering the namespaces with Xpath, using attributes() etc etc. The closest I got was:

$ResponseXml->registerXPathNamespace('xsd','http://www.w3.org/2001/XMLSchema');
$elements = $ResponseXml->xpath('//xsd:element[@minOccurs]');

This actually got me the default namespace attributes, but I need the ones for saw-sql, and the same method of:

$ResponseXml->registerXPathNamespace('saw-sql','urn:saw-sql');
$elements = $ResponseXml->xpath('//saw-sql:element[@columnHeading]');

does not get me any results.

Answers

- ConalTuohy
- February 10, 2023 at 4:04 am
- 0 votes
0
Your XPath //saw-sql:element[@columnHeading] is looking for elements named element (in the saw-sql namespace), which have attributes named columnHeading (in no namespace), but the element names are actually in the xsd namespace, while the attributes are in the saw-sql namespace.

So I believe what you want is:
```
$ResponseXml->registerXPathNamespace('xsd','http://www.w3.org/2001/XMLSchema');
$ResponseXml->registerXPathNamespace('saw-sql','urn:saw-sql');
$elements = $ResponseXml->xpath('//xsd:element[@saw-sql:columnHeading]');
```
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fwiw you could use DOMDocument to parse it instead of SimpleXML, for example

<?php

$xml = <<<'XML'
<?xml version="1.0" encoding="UTF-8" standalone="yes"?><report><QueryResult>
  <ResumptionToken>123456</ResumptionToken>
  <IsFinished>true</IsFinished>
  <ResultXml>
    <rowset xmlns="urn:schemas-microsoft-com:xml-analysis:rowset">
      <xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:saw-sql="urn:saw-sql" targetNamespace="urn:schemas-microsoft-com:xml-analysis:rowset">
        <xsd:complexType name="Row">
          <xsd:sequence>
            <xsd:element maxOccurs="1" minOccurs="1" name="Column0" saw-sql:aggregationRule="none" saw-sql:aggregationType="nonAgg" saw-sql:columnHeading="0" saw-sql:displayFormula="0" saw-sql:length="4" saw-sql:precision="12" saw-sql:scale="0" saw-sql:tableHeading="" saw-sql:type="integer" type="xsd:int"/>
            <xsd:element maxOccurs="1" minOccurs="0" name="Column1" saw-sql:aggregationRule="none" saw-sql:aggregationType="nonAgg" saw-sql:columnHeading="ISBN" saw-sql:displayFormula=""Bibliographic Details"."ISBN"" saw-sql:length="255" saw-sql:precision="255" saw-sql:scale="0" saw-sql:tableHeading="Bibliographic Details" saw-sql:type="varchar" type="xsd:string"/>
            <xsd:element maxOccurs="1" minOccurs="0" name="Column2" saw-sql:aggregationRule="none" saw-sql:aggregationType="nonAgg" saw-sql:columnHeading="ISSN" saw-sql:displayFormula=""Bibliographic Details"."ISSN"" saw-sql:length="255" saw-sql:precision="255" saw-sql:scale="0" saw-sql:tableHeading="Bibliographic Details" saw-sql:type="varchar" type="xsd:string"/>
            <xsd:element maxOccurs="1" minOccurs="0" name="Column3" saw-sql:aggregationRule="none" saw-sql:aggregationType="nonAgg" saw-sql:columnHeading="Publication Date" saw-sql:displayFormula=""Bibliographic Details"."Publication Date"" saw-sql:length="255" saw-sql:precision="255" saw-sql:scale="0" saw-sql:tableHeading="Bibliographic Details" saw-sql:type="varchar" type="xsd:string"/>
          </xsd:sequence>
        </xsd:complexType>
      </xsd:schema>
      <Row>
        <Column0>0</Column0>
        <Column1>55555555 444444445</Column1>
        <Column3>[2019]</Column3>

      </Row>
      <Row>
        <Column0>0</Column0>
        <Column1>555555555</Column1>
        <Column3>©2009.</Column3>
      </Row>
XML;
$domd = new DOMDocument();
@$domd->loadHTML($xml);
foreach ($domd->getElementsByTagName(strtolower("ResultXml")) as $resultXml) {
    $keyNames1 = [];
    $keyNames2 = [];
    foreach ($resultXml->getElementsByTagName("rowset") as $rowset) {
        foreach ($rowset->getElementsByTagName("sequence") as $sequence) {
            foreach ($sequence->getElementsByTagName("element") as $element) {
                $keyNames1[] = $element->getAttribute("name");
                $keyNames2[] = $element->getAttribute(strtolower("saw-sql:columnHeading"));
            }
        }
    }
    $rows = [];
    foreach ($resultXml->getElementsByTagName("row") as $row) {
        $rowData = [];
        foreach ($keyNames1 as $keyName1Key => $keyName1Name) {
            $tmp = $row->getElementsByTagName(strtolower($keyName1Name));
            if ($tmp->length) {
                $rowData[$keyNames2[$keyName1Key]] = $tmp->item(0)->textContent;
            }
        }
        $rows[] = $rowData;
    }
    var_export($rows);
}

yields

array (
  0 =>
  array (
    0 => '0',
    'ISBN' => '55555555 444444445',
    'Publication Date' => '[2019]',
  ),
  1 =>
  array (
    0 => '0',
    'ISBN' => '555555555',
    'Publication Date' => '©2009.',
  ),
)

i used loadHTML instead of loadXML because DOMDocument insists that your XML is not valid XML; in loadHTML() mode, everything is lowercase for some reason, in loadXML() everything is case-sensitive.

SimpleXMLElement::attributes() allows you to access the attributes of a specific namespace providing the namespace URI as a parameter.

$value = $simpleXMLElement->attributes($namespaceURI);

But first I would suggest defining a constant (or variable) for the namespaces that you are using. This will make your code a lot more readable and avoid typos.

Be aware that "rowset" redefines the default namespace for itself and the descendant element nodes, they are not in the "empty/none" namespace.

// define a dictionary for the namespaces
const XMLNS = [
    // same alias as in the document
    'xsd' => 'http://www.w3.org/2001/XMLSchema',
    // let's use a shorter alias
    'saw' => 'urn:saw-sql',
    // own alias - used without alias in the document
    'rowset' => 'urn:schemas-microsoft-com:xml-analysis:rowset'
];

$report = new SimpleXMLElement(getXMLString());
foreach (XMLNS as $alias => $uri) {
    $report->registerXpathNamespace($alias, $uri);
}

$columns = [];
foreach($report->xpath('//xsd:complexType[@name="Row"]/xsd:sequence/xsd:element') as $element) {
    $columns[] = [
        // read the attribute (fallback to '' if missing), cast to string
        'name'=> (string)($element['name'] ?? ''),
        // read attribute with namespace
        'heading'=> (string)($element->attributes(XMLNS['saw'])['columnHeading'] ?? '')
    ];
}

var_dump($columns);

Output:

array(4) {
  [0]=>
  array(2) {
    ["name"]=>
    string(7) "Column0"
    ["heading"]=>
    string(1) "0"
  }
  [1]=>
  array(2) {
    ["name"]=>
    string(7) "Column1"
    ["heading"]=>
    string(4) "ISBN"
  }
  [2]=>
  array(2) {
    ["name"]=>
    string(7) "Column2"
    ["heading"]=>
    string(4) "ISSN"
  }
  [3]=>
  array(2) {
    ["name"]=>
    string(7) "Column3"
    ["heading"]=>
    string(16) "Publication Date"
  }
}

The Xpath Expression

Fetch the type definitions: //xsd:complexType
Filter for "Row": //xsd:complexType[@name="Row"]
The elements inside the sequence:
//xsd:complexType[@name="Row"]/xsd:sequence/xsd:element

The part in [] are conditions for nodes returned the previous location path. So //foo[@bar] would return the foo element nodes with a bar attribute, while //foo/@bar would return the bar attributes of all foo element nodes.

DOM

This solution would not look much different with DOM. The Xpath processor is a separate object and here are specific methods to work with namespaces (suffix "NS"). DOM is more specific and powerful then SimpleXML.

$document = new DOMDocument();
$document->loadXML(getXMLString());
$xpath = new DOMXpath($document);
foreach (XMLNS as $alias => $uri) {
    $xpath->registerNamespace($alias, $uri);
}

$columns = [];
foreach($xpath->evaluate('//xsd:complexType[@name="Row"]/xsd:sequence/xsd:element') as $element) {
    $columns[] = [
        'name'=> $element->getAttribute('name'),
        'heading'=> $element->getAttributeNS(XMLNS['saw'], 'columnHeading')
    ];
} 

var_dump($columns);

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