[译] 在 PHP 中使用 Dom

PHP 中的 HTML 解析是使用的 DOM模块

$dom = new DOMDocument;
$dom->loadHTML($html);
$images = $dom->getElementsByTagName('img');
foreach ($images as $image) {
    $image->setAttribute('src', 'http://example.com/' . $image->getAttribute('src'));
}
$html = $dom->saveHTML();

这里列举所有包含 nofollow 属性的 <a> 标签:

$doc = new DOMDocument();
libxml_use_internal_errors(true);
$doc->loadHTML($html); // loads your HTML
$xpath = new DOMXPath($doc);
// returns a list of all links with rel=nofollow
$nlist = $xpath->query("//a[@rel='nofollow']");

提取谷歌结果的 dom 程序.

<?php
  # Use the Curl extension to query Google and get back a page of results
  $url = "http://www.google.com";
$ch = curl_init();
$timeout = 5;
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, $timeout);
$html = curl_exec($ch);
curl_close($ch);
# Create a DOM parser object
$dom = new DOMDocument();
# Parse the HTML from Google.
# The @ before the method call suppresses any warnings that
# loadHTML might throw because of invalid HTML in the page.
@$dom->loadHTML($html);
# Iterate over all the <a> tags
foreach($dom->getElementsByTagName('a') as $link) {
  # Show the <a href>
  echo $link->getAttribute('href');
  echo "<br />";
}
?>

FAQ

DOMDocument::loadHTML(): Unexpected end tag : p in Entity

当分析 html 代码的时候如果嵌套类型不正确, 则会报这个错误, 因为 <ol> 是一个块级元素, p之内是不能存放任何块级元素的

$html = '<p>
  <ol>
  <li>The OS interface layer has been completely reworked</li>
  </ol>
</p>';
$Dom  = new DOMDocument();
$Dom->loadHTML($html);
$Xpath = new DOMXPath($Dom);
$Xpath->query('//p');

这个 $html在 https://validator.w3.org/ 中进行验证会有如下错误

No p element in scope but a p end tag seen.