Remove xml element node based on index

Question

I have an xml file with many elements, I am looking to remove certain elements based on their indexes.

Sample XML:

<songs>
   <song>
      <title>A</title>
      <artist>AA</artist>
   </song>
</songs>

PHP Code I have so far:

<?php

$index = $_GET['song'];

$doc = new DOMDocument();
$doc->load("songs.xml");
$songs = $doc->getElementsByTagName("song");

foreach($songs as $song) {
    if(in_array($song[$index], $songs)){
        unset($song);
    }
}
$doc->save("songlist.xml");

?>

But I get this error from this code:

Fatal error: Cannot use object of type DOMElement as array

Any help at all is appreciated in this issue, thank you.

@Ghost yes, I am trying to remove the whole song child of songs. — 0xSingularity
– 0xSingularity, Commented Jan 19, 2015 at 5:52

Kevin · Accepted Answer · 2015-01-19 06:09:23Z

1

If your intent is to remove the whole <song> element. Use ->removeChild():

$songs = $doc->getElementsByTagName('song');
$hated_artists = array('AA', 'BB', 'CC');
foreach($songs as $song) {
    $artist = $song->getElementsByTagName('artist')->item(0)->nodeValue;
    if(in_array($artist, $hated_artists)) { // if this song is sang by one of your hated artists
        $song->parentNode->removeChild($song); // remove this song
    }
}

Sample Usage

If you just want a simple criteria, removing by your desired key, then just use the foreach key. Example:

$keys_to_be_removed = array(14, 18);
foreach($songs as $key => $song) {
    if(in_array($key, $keys_to_be_removed)) {
        $song->parentNode->removeChild($song);
    }
}

Or just explicitly using indexing to delete without the foreach loop:

// starts at index zero
$first_song = $doc->getElementsByTagName('song')->item(0);
$songs = $doc->documentElement;
$songs->removeChild($first_song);

edited Jan 19, 2015 at 6:09

answered Jan 19, 2015 at 5:51

Kevin

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3 Comments

0xSingularity Over a year ago

thanks for the tip about the ->removeChild(). But I'm not trying to remove my hated artists. Imagine there are 30 song elements in the songs root element. I just want to remove one of them based on the index. for example songs[14], songs[8], ect. How do I do this?

Kevin Over a year ago

@SunnyD oh okay, just use the foreach key. remember though, this is starts from zero, so the first song will land on index zero. check my edit. i thought you wanted to delete your hated songs/artists, lol

Kevin Over a year ago

@SunnyD i added another piece of info on my revision also, okay, i thought that was your criteria of removing :D, anyways im glad this helped

Mike Loffland · Accepted Answer · 2015-01-19 06:11:15Z

0

$songs = $doc->getElementsByTagName('song');

$songs.item(1).parentNode.removeChild($songs.item(1));
$songs.item(7).parentNode.removeChild($songs.item(7));
$songs.item(12).parentNode.removeChild($songs.item(12));

etc...

edited Jan 19, 2015 at 6:11

answered Jan 19, 2015 at 5:41

Mike Loffland

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1 Comment

0xSingularity Over a year ago

I tried this too but while it got rid of the error, its not deleting the element from the xml file...

ThW · Accepted Answer · 2015-01-19 09:46:18Z

0

XPath can select nodes by their index/position (it starts with 1). It will always return a node list that is traversable with foreach. The list will be empty if the index does not exists. To delete a node from the DOM you have to remove it from its parent node.

$xml = <<<'XML'
<songs>
   <song>
      <title>A</title>
      <artist>AA</artist>
   </song>
</songs>
XML;

$index = 1; // (int)$_GET['song'];

$doc = new DOMDocument();
$doc->loadXml($xml);
$xpath = new DOMXPath($doc);

foreach ($xpath->evaluate('//song['.$index.']') as $song) {
  $song->parentNode->removeChild($song);
}

echo $doc->saveXml();

Output:

<?xml version="1.0"?>
<songs>

</songs>

answered Jan 19, 2015 at 9:46

ThW

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