使用 if 语句通过 Xpath 抓取数据 [英] Using if statement to grab a data with Xpath

问题描述

我有三个 URL，这些 URL 包含我想要的数据.但是每个数据在不同的html标签中.所以这就是为什么我不能为所有人提供相同的 Xpath.我需要尝试如果没有找到这个 Xpath，那么试试这个."就像一种方式.但我对如何做到这一点感到有些困惑?

I have three URL and those URLs have the data that I want. But each data in the different html tag. So that's why I can't give the same Xpath for all. I need to try "if not find it this Xpath then try this." like a way. But i am bit confused to how to do that?

例如，这些是链接$linkBox:

array(3) {
  [0]=>
  string(34) "https://lions-mansion.jp/MF161026/"
  [1]=>
  string(34) "https://lions-mansion.jp/MF171045/"
  [2]=>
  string(34) "https://lions-mansion.jp/MF171010/"
  }

我将一一访问这些链接.对于第一个.我给 Xpath:

And I am going in those links one by one. And for the first one. I am giving Xpath:

$get = [];
    foreach ($linkBox as $box){
        $content = pageContent($box);
            $Pars = new \DOMXPath($content);
            $Route = $Pars->query("//ul[@id='snav']/li/a");
            foreach ($Route as $Rot){
                $get = $Rot->getAttribute('href');
            }

    }

但是那个 Xpath 不适合第二个或第三个.所以用 if 语句如果它是空的我怎么写试试这个?像代码?我能做到吗?或者我需要使用其他方式吗?

But that Xpath doesn't correct for second or third one. So with if statement how can I write if it's null try this? like a code? Can I make it? or Do I need to use another way?

第二个 Box 的 Xpath 是:

The second Box's Xpath is:

 $Route = $Pars->query("//nav[@id='siteActionNav']ul/li/a");

第二个 Box 的 Xpath 是:

The second Box's Xpath is:

 $Route = $Pars->query("//ul[@id='subNavi']/li[2]/a");

推荐答案

您可以做的是尝试每个 XPath 表达式并查看它是否返回任何元素.

What you can do is try out each XPath expression and see if it returns any elements.

例如，这里有一个函数依次测试每个表达式，如果找到任何匹配项，则返回 DOMNodeList，否则抛出异常...

For example, here's a function that tests each expression in turn, returning a DOMNodeList if it finds any matches, throwing an exception otherwise...

function findLinks(\DOMXPath $xp) {
    $queries = [
        '//ul[@id="snav"]/li/a', 
        '//nav[@id="siteActionNav"]ul/li/a', 
        '//ul[@id="subNavi"]/li[2]/a'
    ];
    foreach ($queries as $query) {
        $links = $xp->query($query);
        if ($links->length > 0) {
            return $links; // exits the function and returns the list
        }
    }
    throw new \RuntimeException('No links found');
}

然后你可以像这样使用

foreach ($linkBox as $box){
    $content = pageContent($box);
    try {
        $links = findLinks(new \DOMXPath($content));
        foreach ($links as $link){
            $get[] = $link->getAttribute('href'); // note: changed to a push
        }
    } catch (\Exception $e) {
        echo "Problem with $box: " . $e->getMessage();
    }
}

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