php xml XPath foreach 返回所有节点而不是迭代

Question

I have a XML file like this

<Articles>
 <Article>
  <ArticleTitle> 
   First Book
 </ArticleTitle>
</Article>
 <Article>
  <ArticleTitle> 
   Second Book
 </ArticleTitle>
</Article>

And using this type of php script to retrieve the contents of ArticleTitle in an iterative fashion

foreach ($xml->Article as $Article){
$title = $Article->xpath('//ArticleTitle');
echo $title[0];
}

But this displays

First Book
First Book

Instead of

First Book
Second Book

I was assuming that when the foreach ($xml->Article as $Article) starts it will grab each Article node and then I can access the contents of that node but this is not what is happening. What am I doing wrong?

Answer 1

Your issue is that the xpath you have used is an absolute path (it starts with / ) so the fact that you are calling it from a child node has no effect. You should use a relative path, in this case either simply ArticleTitle will suffice or .//ArticleTitle to allow for other nodes between Article and ArticleTitle . For example:

foreach ($xml->Article as $Article){
    $title = $Article->xpath('ArticleTitle');
    echo $title[0];
}

foreach ($xml->Article as $Article){
    $title = $Article->xpath('.//ArticleTitle');
    echo $title[0];
}

Output in both cases is:

First Book
Second Book

Demo on 3v4l.org

Answer 2

This should work too with your original XPath expression:

$xml = <<<'XML'
<Articles>
<Article>
<ArticleTitle>First Book</ArticleTitle>
</Article>
<Article>
<ArticleTitle>Second Book</ArticleTitle>
</Article>
</Articles>
XML;
$document = new DOMDocument();
$document->loadXML($xml);
$xpath = new DOMXpath($document);
$elements = $xpath->query('//ArticleTitle');
foreach($elements as $element)
echo ($element->nodeValue), "\n";
?>

Output:

First Book
Second Book