php - 为什么 xpath 会删除 html 特殊字符？

Question

为什么会这样

$html = '<a href="/browse/product.do?cid=1&amp;vid=1&amp;pid=1" class="productItemName">what is going on here</a>';

$dom = new DOMDocument();
$dom->loadhtml($html);
$xpath = new DOMXPath($dom);

$selectors['link'] = '//a/@href';
$links_nodeList = $xpath->query($selectors['link']);

foreach ($links_nodeList as $link) {
    $links[] = $link->nodeValue;
}

echo("<p>links</p>");
echo("<pre>");
print_r($links);
echo("</pre>");

输出

links

Array
(
    [0] => /browse/product.do?cid=1&vid=1&pid=1
)

不是

links

Array
(
    [0] => /browse/product.do?cid=1&vid=1&pid=1
)

?

Answer 1

答案很简单:

& 是在 XML 文档中表示字符 "&" 的一种特殊方式。

这两个表示相同的字符。

当 & 符号的转义形式输出为文本(而不是 XML)时，将其显示为 "&" 是正确的。

@LarsH 在他的评论中进一步阐述:

when you say loadhtml($html);, you are parsing the string as HTML, which means that character entities (like &) are interpreted into the characters they represent (like &). If you want a string that will be interpreted as &, you need to escape the ampersand, e.g. &