php Symfony DomCrawler：查找具有特定属性值的元素
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Symfony DomCrawler: Find element with specific attribute value
提问by Wesley
I'm using the DomCrawler component: http://symfony.com/doc/current/components/dom_crawler.html
我正在使用 DomCrawler 组件：http://symfony.com/doc/current/components/dom_crawler.html
I'd like to, using the CSS like syntax, get an element with a specific attribute value.
我想使用类似 CSS 的语法，获取具有特定属性值的元素。
Here's the code I'm using:
这是我正在使用的代码：
$link = $crawler->filter('#product a[data-type="bla"]');
This seems to work, as the following returns 1:
这似乎有效，因为以下返回 1：
echo count($link);
However, I can never not filter further than this. I can not do:
但是，我永远不能比这更进一步过滤。我不能做：
$link->filter('img')->attr('src');
This results in the following error message:
这会导致以下错误消息：
The current node list is empty.
However, I know for certain that it isn't.
但是，我确信它不是。
I've tried the syntax on other elements and it's always the same. I am doing something wrong or is this not possible (with css like syntax, not xpath)
我已经尝试过其他元素的语法，它总是一样的。我做错了什么或者这是不可能的（使用类似 css 的语法，而不是 xpath）
回答by M8R-1jmw5r
I can not follow your problem. Using the current development versions (and also 2.1.0 and 2.2.0 versions) of the twosoftware libraries dom-crawlerand css-selector, the example code you provided works just fine considering the following example HTML:
我无法解决你的问题。使用两个软件库dom-crawler和css-selector的当前开发版本（以及 2.1.0 和 2.2.0 版本），考虑到以下示例 HTML，您提供的示例代码工作得很好：
<?php
use Symfony\Component\DomCrawler\Crawler;
// require dependencies here
$html = <<<'HTML'
<!DOCTYPE html>
<html>
<body>
<p class="message">Hello World!</p>
<p>Hello Crawler!</p>
<div id="product">
<a data-type="bla">
<img src="OK">
</a>
</div>
</body>
</html>
HTML;
$crawler = new Crawler($html);
$link = $crawler->filter('#product a[data-type="bla"]');
echo var_dump(count($link));
var_dump($link->filter('img')->attr('src'));
As you can see this is exactly your code (only a little different but essentially not), which gives the following output verbatim:
正如您所看到的，这正是您的代码（只有一点不同，但基本上没有），它逐字提供以下输出：
int(1)
string(2) "OK"
The first output line is the count()and the second is the src attribute value.
第一个输出行是 the count()，第二个是 src 属性值。
Have you run composer update? Have you double-checked the input?
你有没有运行作曲家更新？您是否仔细检查了输入？
