PHP - 删除XML空节点

Question

I found this code to remove empty nodes from and XML file but it isn't working correctly. It leaves an empty node that really needs to be removed. Yes, it is empty, just white space in it.

$domxml = new DOMDocument('1.0');
$domxml->preserveWhiteSpace = false;
$domxml->formatOutput = true;
$domxml->loadXML($this->response);
$this->response = $domxml->saveXML($domxml->documentElement);

Anyone know of a better way to do this?

Answer 1

In other words you would like to remove any element node that has no text content, no attribute, no children with text content or attributes and have a parent element node (are not the document element).

Here is an Xpath function normalize-space() that converts any whitespace sequences to single spaces and strips them from the start/end. Any whitespace only content will result in an empty string.

Xpath

//* fetches any element node in the document in a list. You just need to add conditions.

• Has no text content
  normalize-space(.) = ""
• No attributes
  not(@*)
• No descendant node with content (includes comments, ...)
  not(.//node()[normalize-space(.) != ""])
• No descendant element nodes with attributes
  not(.//*[@*])
• Has a parent element node
  parent::*

Put together:

$xml = <<<'XML'
<foo>
  <bar></bar>
  <bar>123</bar>
  <bar foo="123"></bar>
  <bar><foo>   </foo></bar>
  <bar><!-- test --></bar>
</foo>
XML;

$document = new DOMDocument();
$document->preserveWhiteSpace = FALSE;
$document->formatOutput = TRUE; 
$document->loadXml($xml);
$xpath = new DOMXpath($document);

$expression = 
  '//*[
    normalize-space(.) = "" and 
    not(@*) and  
    not(.//node()[normalize-space(.) != ""]) and 
    not(.//*[@*]) and
    parent::*
  ]';

$nodes = $xpath->evaluate($expression);
for ($i = $nodes->length - 1; $i >= 0; $i--) {
  $nodes[$i]->parentNode->removeChild($nodes[$i]);
}

echo $document->saveXml();

Output:

<?xml version="1.0"?>
<foo>
  <bar>123</bar>
  <bar foo="123"/>
  <bar>
    <!-- test -->
  </bar>
</foo>