Remove empty tags from a XML with PHP

10
votes

Question

How can I remove empty xml tags in PHP?

Example:

 $value1 = "2";
 $value2 = "4";
 $value3 = "";

 xml = '<parentnode>
        <tag1> ' .$value1. '</tag1>
        <tag2> ' .$value2. '</tag2>
        <tag3> ' .$value3. '</tag3>
       </parentnode>';

XML Result:

<parentnode>
    <tag1>2</tag1>
    <tag2>4</tag2>
    <tag3></tag3> // <- Empty tag
</parentnode>

What I want!

    <parentnode>
            <tag1>2</tag1>
            <tag2>4</tag2> 
    </parentnode>

The XML without the empty tags like "tag3"

Thanks!

5
phpxmltags
Ehm, check if the $value... variables are empty before appending them to the output? - Mr Lister
Yes, thats a way to do it, but I want to make a very clean code with the xml responses. I'm looking for a way to do it with SimpleXMLElement or something like that. - Jimmy

5 Answers

17
votes

You can use XPath with the predicate not(node()) to select all elements that do not have child nodes.

<?php
$doc = new DOMDocument;
$doc->preserveWhiteSpace = false;
$doc->loadxml('<parentnode>
    <tag1>2</tag1>
    <tag2>4</tag2>
    <tag3></tag3>
    <tag2>4</tag2>
    <tag3></tag3>
    <tag2>4</tag2>
    <tag3></tag3>
</parentnode>');

$xpath = new DOMXPath($doc);

foreach( $xpath->query('//*[not(node())]') as $node ) {
    $node->parentNode->removeChild($node);
}

$doc->formatOutput = true;
echo $doc->savexml();

prints 

<?xml version="1.0"?>
<parentnode>
  <tag1>2</tag1>
  <tag2>4</tag2>
  <tag2>4</tag2>
  <tag2>4</tag2>
</parentnode>
7
votes

This works recursively and removes nodes that:

  • contain only spaces
  • do not have attributes
  • do not have child notes
// not(*) does not have children elements
// not(@*) does not have attributes
// text()[normalize-space()] nodes that include whitespace text
while (($node_list = $xpath->query('//*[not(*) and not(@*) and not(text()[normalize-space()])]')) && $node_list->length) {
    foreach ($node_list as $node) {
        $node->parentNode->removeChild($node);
    }
}
5
votes
$dom = new DOMDocument;

$dom->loadXML($xml);

$elements = $dom->getElementsByTagName('*');

foreach($elements as $element) {

   if ( ! $element->hasChildNodes() OR $element->nodeValue == '') {
       $element->parentNode->removeChild($element);
   }

} 

echo $dom->saveXML();

CodePad.

2
votes

The solution that worked with my production PHP SimpleXMLElement object code, by using Xpath, was:

/*
 * Remove empty (no children) and blank (no text) XML element nodes, but not an empty root element (/child::*).
 * This does not work recursively; meaning after empty child elements are removed, parents are not reexamined.
 */
foreach( $this->xml->xpath('/child::*//*[not(*) and not(text()[normalize-space()])]') as $emptyElement ) {
    unset( $emptyElement[0] );
}

Note that it is not required to use PHP DOM, DOMDocument, DOMXPath, or dom_import_simplexml().

//this is a recursively option

do {
    $removed = false;
    foreach( $this->xml->xpath('/child::*//*[not(*) and not(text()[normalize-space()])]') as $emptyElement ) {
        unset( $emptyElement[0] );
        $removed = true;
    }
} while ($removed) ;
0
votes

If you're going to be a lot of this, just do something like:

$value[] = "2";
$value[] = "4";
$value[] = "";   

$xml = '<parentnode>';
for($i=1,$m=count($value); $i<$m+1; $i++)
      $xml .= !empty($value[$i-1]) ? "<tag{$i}>{$value[$i-1]}</tag{$i}>" : null;
$xml .= '</parentnode>';
echo $xml;

Ideally though, you should probably use domdocument.