Remove HTML Tag using DOMDocument

问题

I'd like to remove <font> tags from my html and am trying to use replaceChild to do so, but it doesn't seem to work properly. Can anyone catch what might be wrong?

$html = '<html><body><br><font class="heading2">Limited Size and Resources</font><p><br><strong>Q: When can a member use the limited size and resources exception?</strong></p></body></html>';

$dom = new DOMDocument();
$dom->loadHTML($html);
$font_tags = $dom->GetElementsByTagName('font');

foreach($font_tags as $font_tag) {
  foreach($font_tag as $child) {
    $child->replaceChild($child->nodeValue, $font_tag);
  }
}

echo $dom->saveHTML();

From what I understand, $font_tags is a DOMNodeList, so I need to iterate through it twice in order to use the DOMNode::replaceChild function. I then want to replace the current value with just the content inside of the tags. However, when I output the $html nothing changes. Any ideas what could be wrong?

Here is a PHP Sandbox to test the code.

回答1:

I'll put my remarks inline

$html = '<html><body><br><font class="heading2">Limited Size and Resources</font><p><br><strong>Q: When can a member use the limited size and resources exception?</strong></p></body></html>';

$dom = new DOMDocument();
$dom->loadHTML($html);
$font_tags = $dom->GetElementsByTagName('font');

/* You only need one loop, as it is iterating your collection 
   You would only need a second loop if each font tag had children of their own
*/
foreach($font_tags as $font_tag) {
  /* replaceChild replaces children of the node being called
     So, to replace the font tag, call the function on its parent
     $prent will be that reference
  */
  $prent = $font_tag->parentNode;
   /* You can't insert arbitrary text, you have to create a textNode
      That textNode must also be a member of your document
   */
  $prent->replaceChild($dom->createTextNode($font_tag->nodeValue), $font_tag);

}

echo $dom->saveHTML();

Updated Sandbox: Hopefully I understood your requirements correctly

回答2:

First, let us find out what wasn't working in your code.

foreach($font_tag as $child) wasn't even iterating once as $font_tag is a single 'font' tag element from font_tags array, and not an array itself.
$child->replaceChild($child->nodeValue, $font_tag); - A child node can't replace its parent ($font_tag), but the reverse is possible. As replaceChild is a method of the parent node to replace its child.
For more details check the PHP: DOMNode::replaceChild documentation, or the point 2 below my code.
echo $html will output the $html string, but not the updated $dom object that we are modifying.

This would work -

$html = '<html><body><br><font class="heading2">Limited Size and Resources</font><p><br><strong>Q: When can a member use the limited size and resources exception?</strong></p></body></html>';

$dom = new DOMDocument();
$dom->loadHTML($html);
$font_tags = $dom->GetElementsByTagName('font');

foreach($font_tags as $font_tag)
{
    $new_node = $dom->createTextNode($font_tag->nodeValue);
    $font_tag->parentNode->replaceChild($new_node, $font_tag);
}

echo $dom->saveHTML();

I am creating a $new_node directly in the $dom, so the node is live in the DOMDocument and not any local variable.
To replace the child object $font_tag, we have to first traverse to the parent node using the parentNode method.
Finally, we are printing out the modified $dom using saveHTML method, which will convert the DOMDocument into a HTML String.

来源：https://stackoverflow.com/questions/25632240/remove-html-tag-using-domdocument

标签

php

html

domdocument