如何使用PHP的SimpleXML扩展遍历XML树？

Question

Given the following XML:

$xmlstr = <<<XML
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <soap:Body>
    <DataService xmlns="http://www.example.com">
      <Response>
        <XMLRootNode xmlns="http://www.example.com">
          <ResponseHeader>
            <Version>2.0</Version>
            <RecordCount>2</RecordCount>
          </ResponseHeader>
          <OnlineInformation BoothID="12345">
            <EventID>4</EventID>
            ...

How can I access the contents of EventID using PHP's SimpleXML extension? I've had success with a simple example form here, but I cannot seem to traverse the more complex tree structure above. My basic code is below. I want $output to contain the value 4.

$data = new SimpleXMLElement($xmlstr);

$output = $data->...

Thanks.

Answer 1

You can alternatively you DOMDocument. Like this:

// your incomplete xml sample
$xmlstr = <<<XML
<?xml version="1.0" encoding="utf-8"?>
  <soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <soap:Body>
      <DataService xmlns="http://www.example.com">
        <Response>
          <XMLRootNode xmlns="http://www.example2.com">
            <ResponseHeader>
              <Version>2.0</Version>
              <RecordCount>2</RecordCount>
            </ResponseHeader>
            <OnlineInformation ExampleID="12345">
              <EventID>4</EventID>
            </OnlineInformation>
          </XMLRootNode>    
        </Response>
      </DataService>
    </soap:Body>
  </soap:Envelope>
XML;

$dom = new DOMDocument();
$dom->loadXML($xmlstr);
foreach($dom->getElementsByTagName('OnlineInformation') as $OnlineInformation) {
    if($OnlineInformation->getAttribute('ExampleID') == 12345) {
        echo $OnlineInformation->getElementsByTagName('EventID')->item(0)->nodeValue;
        // 4
    }
}

Or just use xpath and directly point it:

$xml = simplexml_load_string($xmlstr);
$xml->registerXPathNamespace('ns', 'http://www.example2.com');
$node = $xml->xpath('//ns:OnlineInformation[@ExampleID="12345"]')[0];
echo (string) $node->EventID; // 4