使用正则表达式匹配未嵌套在锚标记中的图像标记 [英] Match image tag not nested in an anchor tag using regular expression

问题描述

如何使用正则表达式匹配未嵌套在锚标记内的图像?

How would I match images that is not nested inside an anchor tag using regular expression?

这是我想要的:

不匹配: <a href="index.html"><img src="images/default.jpg"/></a>

匹配: <div><img src="images/default.jpg"/></div>

匹配: <img src="images/default.jpg"/>

我不擅长正则表达式，但这是我目前想到的，但不起作用:

I'm no good at regex but this is what I came up so far, which doesn't work:

[^]

我无法使用环视，因为 PHP 希望它是具体的.

I couldn't use lookarounds since PHP wants it to be specific.

推荐答案

您遇到困难的大部分原因很简单，HTML 不是常规语言，请参阅:编码恐怖:以克苏鲁方式解析 Html

Much of the reason behind your difficulty is simply that HTML is not a regular language, see: Coding Horror: Parsing Html the Cthulhu Way

考虑使用足够强大的查询表达式语言来处理 (X)HTML，或者仅以编程方式使用 DOM 来获取所有图像标签，然后排除那些具有 祖先的标签.

Consider using a query expression language powerful enough to process (X)HTML, or just using the DOM programmatically to fetch all image tags and then exclude those with <a> ancestors.

在 PHP5 中，我相信你可以使用 DOMXPath，使用它变得如此简单:

In PHP5, I believe you can use DOMXPath, using that it becomes as simple as:

$generated_string = '<a href="index.html"><img src="images/inside_a.jpg" /></a>' .
                    '<div><img src="images/inside_div.jpg" /></div>' .
                    '<img src="images/inside_nothing.jpg" />';

$doc = new DOMDocument();
$doc->loadHTML($generated_string);
$xpath = new DOMXpath($doc);

$elements = $xpath->query("//*[not(self::a)]/img");

foreach ($elements as $element){
  echo $doc->saveXML($element) . "\n";
}

此代码将给出输出:

<img src="images/inside_div.jpg"/>
<img src="images/inside_nothing.jpg"/>

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