Xpath with html5lib in PHP - php

Question

I have this basic code that doesn't work. How can I use Xpath with html5lib php? Or Xpath with HTML5 in any other way.
$url = 'http://en.wikipedia.org/wiki/PHP';
$response = GuzzleHttp\get($url);
$html5 = new Masterminds\HTML5();
$dom = $html5->loadHTML($response);
$xpath = new DOMXPath($dom);
$elements = $xpath->query('//h1');
//$elements = $dom->getElementsByTagName('h1');
foreach ($elements as $element)
{
var_dump($element);
}
No elements are found. Using $xpath->query('.') works for getting the root element (xpath in general seems to work). $dom->getElementsByTagName('h1') is working.

Answer 1

use disable_html_ns option.
$url = 'http://en.wikipedia.org/wiki/PHP';
$response = GuzzleHttp\get($url)->getBody();
$html5 = new Masterminds\HTML5(array(
'disable_html_ns' => true, // add `disable_html_ns` option
));
$dom = $html5->loadHTML($response);
$xpath = new DOMXPath($dom);
$elements = $xpath->query('//h1');
foreach ($elements as $element) {
var_dump($element);
}
https://github.com/Masterminds/html5-php#options
disable_html_ns (boolean): Prevents the parser from automatically assigning the HTML5 namespace to the DOM document. This is for non-namespace aware DOM tools.

Answer 2

So it looks like html5lib is setting us up with a default namespace.
$url = 'http://en.wikipedia.org/wiki/PHP';
$response = GuzzleHttp\get($url)->getBody();
$html5 = new Masterminds\HTML5();
$dom = $html5->loadHTML($response);
$de = $dom->documentElement;
if ($de->isDefaultNamespace($de->namespaceURI)) {
echo $de->namespaceURI . "\n";
}
This outputs:
http://www.w3.org/1999/xhtml
To query against namespaced nodes with xpath you need to register the namespace and use the prefix in the query.
$xpath = new DOMXPath($dom);
$xpath->registerNamespace('n', $de->namespaceURI);
$elements = $xpath->query('//n:h1');
foreach ($elements as $element)
{
echo $element->nodeValue;
}
This outputs PHP.
Generally I find it tedious to prefix everything in xpath queries when there's a default namespace involved, so I just strip it.
$de = $dom->documentElement;
$de->removeAttributeNS($de->getAttributeNode("xmlns")->nodeValue,"");
$dom->loadXML($dom->saveXML()); // reload the existing dom, now sans default ns
After that you can use your original xpath and it'll work just fine.
$elements = $xpath->query('//h1');
foreach ($elements as $element)
{
echo $element->nodeValue;
}
This now outputs PHP as well.
So the modified version of the example would be something like:
Example:
$url = 'http://en.wikipedia.org/wiki/PHP';
$response = GuzzleHttp\get($url)->getBody();
$html5 = new Masterminds\HTML5();
$dom = $html5->loadHTML($response);
$de = $dom->documentElement;
if ($de->isDefaultNamespace($de->namespaceURI)) {
$de->removeAttributeNS($de->getAttributeNode("xmlns")->nodeValue,"");
$dom->loadXML($dom->saveXML());
}
$xpath = new DOMXPath($dom);
$elements = $xpath->query('//h1');
foreach ($elements as $element)
{
var_dump($element);
}
Output:
class DOMElement#11 (18) {
public $tagName =>
string(2) "h1"
public $schemaTypeInfo =>
NULL
public $nodeName =>
string(2) "h1"
public $nodeValue =>
string(3) "PHP"
...
public $textContent =>
string(3) "PHP"
}