How do you parse and process HTML/XML in PHP?-第5页回答

2楼-- · 2018-12-31 00:56

There are many ways to process HTML/XML DOM of which most have already been mentioned. Hence, I won't make any attempt to list those myself.

I merely want to add that I personally prefer using the DOM extension and why :

iit makes optimal use of the performance advantage of the underlying C code
it's OO PHP (and allows me to subclass it)
it's rather low level (which allows me to use it as a non-bloated foundation for more advanced behavior)
it provides access to every part of the DOM (unlike eg. SimpleXml, which ignores some of the lesser known XML features)
it has a syntax used for DOM crawling that's similar to the syntax used in native Javascript.

And while I miss the ability to use CSS selectors for DOMDocument, there is a rather simple and convenient way to add this feature: subclassing the DOMDocument and adding JS-like querySelectorAll and querySelector methods to your subclass.

For parsing the selectors, I recommend using the very minimalistic CssSelector component from the Symfony framework. This component just translates CSS selectors to XPath selectors, which can then be fed into a DOMXpath to retrieve the corresponding Nodelist.

You can then use this (still very low level) subclass as a foundation for more high level classes, intended to eg. parse very specific types of XML or add more jQuery-like behavior.

The code below comes straight out my DOM-Query library and uses the technique I described.

For HTML parsing :

namespace PowerTools;

use \Symfony\Component\CssSelector\CssSelector as CssSelector;

class DOM_Document extends \DOMDocument {
    public function __construct($data = false, $doctype = 'html', $encoding = 'UTF-8', $version = '1.0') {
        parent::__construct($version, $encoding);
        if ($doctype && $doctype === 'html') {
            @$this->loadHTML($data);
        } else {
            @$this->loadXML($data);
        }
    }

    public function querySelectorAll($selector, $contextnode = null) {
        if (isset($this->doctype->name) && $this->doctype->name == 'html') {
            CssSelector::enableHtmlExtension();
        } else {
            CssSelector::disableHtmlExtension();
        }
        $xpath = new \DOMXpath($this);
        return $xpath->query(CssSelector::toXPath($selector, 'descendant::'), $contextnode);
    }

    [...]

    public function loadHTMLFile($filename, $options = 0) {
        $this->loadHTML(file_get_contents($filename), $options);
    }

    public function loadHTML($source, $options = 0) {
        if ($source && $source != '') {
            $data = trim($source);
            $html5 = new HTML5(array('targetDocument' => $this, 'disableHtmlNsInDom' => true));
            $data_start = mb_substr($data, 0, 10);
            if (strpos($data_start, '<!DOCTYPE ') === 0 || strpos($data_start, '<html>') === 0) {
                $html5->loadHTML($data);
            } else {
                @$this->loadHTML('<!DOCTYPE html><html><head><meta charset="' . $encoding . '" /></head><body></body></html>');
                $t = $html5->loadHTMLFragment($data);
                $docbody = $this->getElementsByTagName('body')->item(0);
                while ($t->hasChildNodes()) {
                    $docbody->appendChild($t->firstChild);
                }
            }
        }
    }

    [...]
}

See also Parsing XML documents with CSS selectors by Symfony's creator Fabien Potencier on his decision to create the CssSelector component for Symfony and how to use it.

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余欢

3楼-- · 2018-12-31 00:56

If you're familiar with jQuery selector, you can use ScarletsQuery for PHP

<pre><?php
include "ScarletsQuery.php";

// Load the HTML content and parse it
$html = file_get_contents('https://www.lipsum.com');
$dom = Scarlets\Library\MarkupLanguage::parseText($html);

// Select meta tag on the HTML header
$description = $dom->selector('head meta[name="description"]')[0];

// Get 'content' attribute value from meta tag
print_r($description->attr('content'));

$description = $dom->selector('#Content p');

// Get element array
print_r($description->view);

This library usually taking less than 1 second to process offline html.
It also accept invalid HTML or missing quote on tag attributes.

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其实，你不懂

4楼-- · 2018-12-31 00:58

I've created a library called HTML5DOMDocument that is freely available at https://github.com/ivopetkov/html5-dom-document-php

It supports query selectors too that I think will be extremely helpful in your case. Here is some example code:

$dom = new IvoPetkov\HTML5DOMDocument();
$dom->loadHTML('<!DOCTYPE html><html><body><h1>Hello</h1><div class="content">This is some text</div></body></html>');
echo $dom->querySelector('h1')->innerHTML;

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春风洒进眼中

5楼-- · 2018-12-31 00:59

Just use DOMDocument->loadHTML() and be done with it. libxml's HTML parsing algorithm is quite good and fast, and contrary to popular belief, does not choke on malformed HTML.

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深知你不懂我心

6楼-- · 2018-12-31 00:59

Why you shouldn't and when you should use regular expressions?

First off, a common misnomer: Regexps are not for "parsing" HTML. Regexes can however "extract" data. Extracting is what they're made for. The major drawback of regex HTML extraction over proper SGML toolkits or baseline XML parsers are their syntactic effort and varying reliability.

Consider that making a somewhat dependable HTML extraction regex:

<a\s+class="?playbutton\d?[^>]+id="(\d+)".+?    <a\s+class="[\w\s]*title
[\w\s]*"[^>]+href="(http://[^">]+)"[^>]*>([^<>]+)</a>.+?

is way less readable than a simple phpQuery or QueryPath equivalent:

$div->find(".stationcool a")->attr("title");

There are however specific use cases where they can help.

Many DOM traversal frontends don't reveal HTML comments <!--, which however are sometimes the more useful anchors for extraction. In particular pseudo-HTML variations <$var> or SGML residues are easy to tame with regexps.
Oftentimes regular expressions can save post-processing. However HTML entities often require manual caretaking.
And lastly, for extremely simple tasks like extracting <img src= urls, they are in fact a probable tool. The speed advantage over SGML/XML parsers mostly just comes to play for these very basic extraction procedures.

It's sometimes even advisable to pre-extract a snippet of HTML using regular expressions /(.+?)/ and process the remainder using the simpler HTML parser frontends.

Note: I actually have this app, where I employ XML parsing and regular expressions alternatively. Just last week the PyQuery parsing broke, and the regex still worked. Yes weird, and I can't explain it myself. But so it happened.
So please don't vote real-world considerations down, just because it doesn't match the regex=evil meme. But let's also not vote this up too much. It's just a sidenote for this topic.

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How do you parse and process HTML/XML in PHP?

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