仅从 RSS 提要解析 img src 时遇到问题？

Question

我正在尝试根据以下示例创建 RSS reader：

http://www.w3schools.com/php/php_ajax_rss_reader.asp

具体来说，我正在尝试修改此示例，以便 reader 可以访问并显示来自任何给定网络漫画 RSS 提要的所有可用漫画图像（仅此而已）。我意识到可能有必要使代码至少有一点特定于站点，但我正在努力使其尽可能通用。目前，我已经修改了初始示例以生成一个 reader 来显示给定 RSS 提要列表的所有漫画。但是，它还会显示我试图摆脱的其他不需要的文本信息。到目前为止，这是我的代码，有一些提要特别给我带来麻烦：

index.php 文件:

<html>
<head>
    <script>
        function showRSS() 
        {
          if (window.XMLHttpRequest) 
          {
            // code for IE7+, Firefox, Chrome, Opera, Safari
            xmlhttp=new XMLHttpRequest();
          } else 
          {  // code for IE6, IE5
            xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
          }
          xmlhttp.onreadystatechange=function() 
          {
            if (xmlhttp.readyState==4 && xmlhttp.status==200) 
            {
              document.getElementById("rssOutput").innerHTML=xmlhttp.responseText;
            }
          }
          xmlhttp.open("GET","logger.php",true);
          xmlhttp.send();
        }
    </script>
</head>
<body onload="showRSS()">
    <div id="rssOutput"></div>
</body>
</html>

（很确定这个文件没有问题；我认为问题出现在下一个文件中，尽管我为了完整性而包含了这个文件）

logger.php:

<?php

//function to get all comics from an rss feed
function getComics($xml)
{
    $xmlDoc = new DOMDocument();
    $xmlDoc->load($xml);

    $x=$xmlDoc->getElementsByTagName('item');
    foreach ($x as $x)
    {
      $comic_image=$x->getElementsByTagName('description')->item(0)->childNodes->item(0)->nodeValue;
      //output the comic
      echo ($comic_image . "</p>");
      echo ("<br>");
    }

}

//create array of all RSS feed URLs
$URLs =
[
    "SMBC" => "http://www.smbc-comics.com/rss.php", 
    "garfieldMinusGarfield" => "http://garfieldminusgarfield.net/rss",
    "babyBlues" => "http://www.comicsyndicate.org/Feed/Baby%20Blues",
];

//Loop through all RSS feeds
foreach ($URLs as $xml)
{
    getComics($xml);
}

?>

因为此方法在漫画图像之间包含额外的文本（SMBC 有很多随机内容，gMg 只是一些广告 link，婴儿布鲁斯的版权 link），我查看了 RSS 提要并得出结论，问题在于它是包含图像源的描述标签，但还包含其他内容。接下来，我尝试修改 getComics 函数以直接扫描图像标签，而不是首先查找描述标签。我将 DOMDocument creation/loading 和 URL 列表之间的部分替换为：

$images=$xmlDoc->getElementsByTagName('img');
    print_r($images);

    foreach ($images as $image)
    {
        //echo $image->item(0)->getAttribute('src');
        echo $image->item(0)->nodeValue;
        echo ("<br>");
    }

但显然 getElementsByTagName 没有获取描述标签内嵌入的图像标签，因为我没有输出任何漫画图像，print_r 语句的输出如下：

DOMNodeList Object ( [length] => 0 ) DOMNodeList Object ( [length] => 0 )

最后，我尝试了两种方法的组合，尝试在解析出描述标签内容的代码中使用getElementsByTagNam('img')。我替换了行：

$comic_image=$x->getElementsByTagName('description')->item(0)->childNodes->item(0)->nodeValue;

与：

$comic_image=$x->getElementsByTagName('description')->item(0)->getElementsByTagName('img');
      print_r($comic_image);

但这也什么也没找到，产生输出：

DOMNodeList Object ( [length] => 0 )

很抱歉背景很长，但我想知道是否有一种方法可以只从给定的 RSS 提要中解析 img src 而没有其他文本和 links 我不知道想要？

不胜感激

Answer 1

在内部，描述内容被转义，所以下面的代码应该可以工作：

foreach ($x as $y) {
    $description = $y->getElementsByTagName('description')->item(0);
    $decoded_description = htmlspecialchars_decode($description->nodeValue);
    $description_xml = new DOMDocument();
    $description_xml->loadHTML($decoded_description);
    $comic_image = $description_xml->getElementsByTagName('img')->item(0)->getAttribute('src');

    //output the comic
    echo ($comic_image);
    echo ("<br>");
}

Answer 2

供以后阅读此论坛的其他人参考，这是我最终得到的代码。我用调用 getImageTag 函数的 getImageSrc 函数替换了 for each 循环中的所有内容：

//function to find an image tag within a specific section if there is one
function getImageTag ($item,$tagName)
{
    //pull desired section from given item
    $section = $item->getElementsByTagName($tagName)->item(0);
    //reparse description as if it were a string, because for some reason  PHP woon't let you directly go to the source image with getElementsByTagName
    $decoded_section = htmlspecialchars_decode($section->nodeValue);
    $section_xml = new DOMDocument();
    @$section_xml->loadHTML($decoded_section); //the @ is to suppress a bunch of warnings about characters this parser doesn't like
    //pull image tag from section if there
    $image_tag = $section_xml->getElementsByTagName('img')->item(0);
    return $image_tag;
}

//function to get the image source URL from a given item
function getImageSrc ($item)
{
    $image_tag = getImageTag($item,'description');
    if (is_null($image_tag)) //if there was nothing with the tag name of  image in the description section
    {
        //check in content:encoded section, because that's the next most likely place
        $image_tag = getImageTag($item,'encoded');
        if (is_null($image_tag)) //if there was nothing with the tag name of image in the encoded content section
        {
            //if the program gets here,  it's probably because the feed is crap and doesn't include images,
            //or it's because this particular item doesn't have a comic image in it
            $image_src = '';
            //THIS EXCEPTION  WILL PROBABLY NEED TO BE HANDLED LATER TO AVOID POTENTIAL ERRORS
        } else
        {
            $image_src = $image_tag->getAttribute('src');
        }
    } else
    {
        $image_src = $image_tag->getAttribute('src');
    }
    return $image_src;
}

仅从 RSS 提要解析 img src 时遇到问题？

Trouble parsing just img src from RSS feed?

php

rss

dom