Getting DOM elements by classname
I'm using PHP DOM and I'm trying to get an element within a DOM node that have a given class name. What's the best way to get that sub-element?
开发者_开发知识库Update: I ended up using Mechanize for PHP which was much easier to work with.
Update: Xpath version of *[@class~='my-class'] css selector
So after my comment below in response to hakre's comment, I got curious and looked into the code behind Zend_Dom_Query. It looks like the above selector is compiled to the following xpath (untested):
[contains(concat(' ', normalize-space(@class), ' '), ' my-class ')]
So the PHP would be:
$dom = new DomDocument();
$dom->load($filePath);
$finder = new DomXPath($dom);
$classname="my-class";
$nodes = $finder->query("//*[contains(concat(' ', normalize-space(@class), ' '), ' $classname ')]");
Basically, all we do here is normalize the class attribute so that even a single class is bounded by spaces, and the complete class list is bounded in spaces. Then append the class we are searching for with a space. This way we are effectively looking for and find only instances of my-class .
Use an xpath selector?
$dom = new DomDocument();
$dom->load($filePath);
$finder = new DomXPath($dom);
$classname="my-class";
$nodes = $finder->query("//*[contains(@class, '$classname')]");
If it is only ever one type of element you can replace the * with the particular tagname.
If you need to do a lot of this with very complex selector I would recommend Zend_Dom_Query which supports CSS selector syntax (a la jQuery):
$finder = new Zend_Dom_Query($html);
$classname = 'my-class';
$nodes = $finder->query("*[class~=\"$classname\"]");
If you wish to get the innerhtml of the class without the zend you could use this:
$dom = new DomDocument();
$dom->load($filePath);
$classname = 'main-article';
$finder = new DomXPath($dom);
$nodes = $finder->query("//*[contains(concat(' ', normalize-space(@class), ' '), ' $classname ')]");
$tmp_dom = new DOMDocument();
foreach ($nodes as $node)
{
$tmp_dom->appendChild($tmp_dom->importNode($node,true));
}
$innerHTML.=trim($tmp_dom->saveHTML());
echo $innerHTML;
I think the accepted way is better, but I guess this might work as well
function getElementByClass(&$parentNode, $tagName, $className, $offset = 0) {
$response = false;
$childNodeList = $parentNode->getElementsByTagName($tagName);
$tagCount = 0;
for ($i = 0; $i < $childNodeList->length; $i++) {
$temp = $childNodeList->item($i);
if (stripos($temp->getAttribute('class'), $className) !== false) {
if ($tagCount == $offset) {
$response = $temp;
break;
}
$tagCount++;
}
}
return $response;
}
There is also another approach without the use of DomXPath or Zend_Dom_Query.
Based on dav's original function, I wrote the following function that returns all the children of the parent node whose tag and class match the parameters.
function getElementsByClass(&$parentNode, $tagName, $className) {
$nodes=array();
$childNodeList = $parentNode->getElementsByTagName($tagName);
for ($i = 0; $i < $childNodeList->length; $i++) {
$temp = $childNodeList->item($i);
if (stripos($temp->getAttribute('class'), $className) !== false) {
$nodes[]=$temp;
}
}
return $nodes;
}
suppose you have a variable $html the following HTML:
<html>
<body>
<div id="content_node">
<p class="a">I am in the content node.</p>
<p class="a">I am in the content node.</p>
<p class="a">I am in the content node.</p>
</div>
<div id="footer_node">
<p class="a">I am in the footer node.</p>
</div>
</body>
</html>
use of getElementsByClass is as simple as:
$dom = new DOMDocument('1.0', 'utf-8');
$dom->loadHTML($html);
$content_node=$dom->getElementById("content_node");
$div_a_class_nodes=getElementsByClass($content_node, 'div', 'a');//will contain the three nodes under "content_node".
DOMDocument is slow to type and phpQuery has bad memory leak issues. I ended up using:
https://github.com/wasinger/htmlpagedom
To select a class:
include 'includes/simple_html_dom.php';
$doc = str_get_html($html);
$href = $doc->find('.lastPage')[0]->href;
I hope this helps someone else as well
PHP's native DOM handling is so absurdly bad, do yourself a favour and use this or any other modern HTML parsing package which can handle this within in few lines:
Install paquettg/php-html-parser with
composer require paquettg/php-html-parser
Then create a .php file in the same folder with this content
<?php
// load dependencies via Composer
require __DIR__ . '/vendor/autoload.php';
use PHPHtmlParser\Dom;
$dom = new Dom;
$dom->loadFromUrl("https://example.com");
$links = $dom->find('.classname a');
foreach ($links as $link) {
echo $link->getAttribute('href');
}
P.S. You'll find information on how to install Composer on Composer's homepage.
I prefer using Symfony for this. Their libraries are pretty nice.
Use the The DomCrawler Component
Example:
$browser = new HttpBrowser(HttpClient::create());
$crawler = $browser->request('GET', 'example.com');
$class = $crawler->filter('.class')->first();
加载中,请稍侯......
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