php - How do I do an XPath query on a DOMNode?

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php - How do I do an XPath query on a DOMNode?

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

Is there a way to do an xpath query on a DOMNode? Or at least convert it to a DOMXPath?

<html>
  ...
  <div id="content">
     ...
     <div class="listing">
         ...
         <div></div>
         <div></div>
         <div  class='foo'>
           <h3>Get me 1</h3>
           <a>and me too 1</a>
         </div>
     </div>
     <div class="listing">
         ...
         <div></div>
         <div></div>
         <div class='foo'>
           <h3>Get me 2</h3>
           <a>and me too 1</a>
         </div>
     </div>
     ....
  </div>
</html>

This is my code. I am trying to get a list of array that has the values of the h3 and a tags in each array. To do that, I needed to get each listing, and then get the h3 and a tag's value in each listing.

$html_dom = new DOMDocument();
@$html_dom->loadHTML($html);
$x_path = new DOMXPath($html_dom);

$nodes= $x_path->query("//div[@id='content']//div[@class='listing']");

foreach ($nodes as $node)
{
  // I want to further dig down here using query on a DOMNode
}

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1 Answer

深蓝 · Answer 1 · 2021-10-23T17:53:33+0000

Pass the node as the second argument to DOMXPath::query

contextnode: The optional contextnode can be specified for doing relative XPath queries. By default, the queries are relative to the root element.

Example:

foreach ($nodes as $node) {
    foreach ($x_path->query('h3|a', $node) as $child) {
        echo $child->nodeValue, PHP_EOL;
    }
}

This uses the UNION operator for a result of

Get me 1
and me too 1
Get me 2
and me too 1

If you don't need any complex querying, you can also do

foreach ($nodes as $node) {
    foreach ($node->getElementsByTagName('a') as $a) {
      echo $a->nodeValue, PHP_EOL;
    }
}

Or even by iterating the child nodes (note that this includes all the text nodes)

foreach ($nodes as $node) {
    foreach ($node->childNodes as $child) {
      echo $child->nodeName, PHP_EOL;
    }
}

However, all of that is unneeded since you can fetch these nodes directly:

$nodes= $x_path->query("/html/body//div[@class='listing']/div[last()]");

foreach ($nodes as $i => $node) {
    echo $i, $node->nodeValue, PHP_EOL;
}

will give you two nodes in the last div child of all the divs with a class attribute value of listing and output the combined text node values, including whitespace

0
           Get me 1
           and me too 1

1
           Get me 2
           and me too 1

Likewise, the following

"//div[@class='listing']/div[last()]/node()[name() = 'h3' or name() = 'a']"

will give you the four child H3 and A nodes and output

0Get me 1
1and me too 1
2Get me 2
3and me too 1

If you need to differentiate these by name while iterating over them, you can do

foreach ($nodes as $i => $node) {
    echo $i, $node->nodeName, $node->nodeValue, PHP_EOL;
}

which will then give

0h3Get me 1
1aand me too 1
2h3Get me 2
3aand me too 1

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