xml parsing - DOMDocument in php

Question

I have just started reading documentation and examples about DOM, in order to crawl and parse the document.

For example I have part of document shown below:

    <div id="showContent">
    <table>
    <tr>
        <td>
         Crap
        </td>
    </tr>
<tr>
          <td width="172" valign="top"><a href="link"><img height="91" border="0" width="172" class="" src="img"></a></td>
          <td width="10">&nbsp;</td>
          <td valign="top"><table cellspacing="0" cellpadding="0" border="0">
              <tbody><tr>
                <td height="30"><a class="px11" href="link">title</a><a><br>
                    <span class="px10"></span>
                </a></td>
              </tr>
              <tr>
                <td><img height="1" width="580" src="crap"></td>
              </tr>
              <tr>
                <td align="right">
                    <a href="link"><img height="16" border="0" width="65" src="/buy"></a>
                </td>
              </tr>
              <tr>
                <td valign="top" class="px10">
                    <p style="width: 500px;">description.</p>
                </td>
              </tr>
          </tbody></table></td>
        </tr>
    <tr>
        <td>
Crap
        </td>
    </tr>
    <tr>
        <td>
         Crap
        </td>
    </tr>
    </table>
    </div>

I'm trying to use the following code to get all the tr tags and analyze whether there is crap or information inside them:

$dom = new DOMDocument();
@$dom->loadHTML($html);

$xpath = new DOMXPath($dom);


$tags = $xpath->query('.//div[@id="showContent"]');
foreach ($tags as $tag) {
    $string="";
    $string=trim($tag->nodeValue);
    if(strlen($string)>3) {
        echo $string;
        echo '<br>';
    }
}

However I'm getting just stripped string without the tags, for example:

Crap

Crap
Title
Description

But I would like to get:

<tr>
   <td>Crap</td>
</tr>
<tr>
   <a href="link">title</a>
</tr>

How to keep html nodes (tags)?

Answer 1

If you want to work with DOM you have to understand the concept. Everything in a DOM Document, including the DOMDocument, is a Node.

The DOMDocument is a hierarchical tree structure of nodes. It starts with a root node. That root node can have child nodes and all these child nodes can have child nodes on their own. Basically everything in a DOMDocument is a node type of some sort, be it elements, attributes or text content.

          HTML                               Legend: 
         /                                  UPPERCASE = DOMElement
       HEAD  BODY                            lowercase = DOMAttr
      /                                     "Quoted"  = DOMText
    TITLE        DIV - class - "header"
     |             
"The Title"        H1
                    |
           "Welcome to Nodeville"

The diagram above shows a DOMDocument with some nodes. There is a root element (HTML) with two children (HEAD and BODY). The connecting lines are called axes. If you follow down the axis to the TITLE element, you will see that it has one DOMText leaf. This is important because it illustrates an often overlooked thing:

<title>The Title</title>

is not one, but two nodes. A DOMElement with a DOMText child. Likewise, this

<div class="header">

is really three nodes: the DOMElement with a DOMAttr holding a DOMText. Because all these inherit their properties and methods from DOMNode, it is essential to familiarize yourself with the DOMNode class.

In practise, this means the DIV you fetched is linked to all the other nodes in the document. You could go all the way to the root element or down to the leaves at any time. It's all there. You just have to query or traverse the document for the wanted information.

Whether you do that by iterating the childNodes of the DIV or use getElementByTagName() or XPath is up to you. You just have to understand that you are not working with raw HTML, but with nodes representing that entire HTML document.

If you need help with extracting specific information from the document, you need to clarify what information you want to fetch from it. For instance, you could ask how to fetch all the links from the table and then we could answer something like:

$div = $dom->getElementById('showContent');
foreach ($div->getElementsByTagName('a') as $link) 
{
    echo $dom->saveXML($link);
}

But unless you are more specific, we can only guess which nodes might be relevant.

If you need more examples and code snippets on how to work with DOM browse through my previous answers to related questions:

• https://stackoverflow.com/search?q=user%3A208809+DOM

By now, there should be a snippet for every basic to medium UseCase you might have with DOM.