simple inserting of XML line using PHP

Easiest way to do that would be to use PHP's DOM support
http://us2.php.net/manual/en/ref.dom.php

<?php
$xml = new DOMDocument;
$xml->loadXML($song_xml); /*where song_xml is the xml you provided*/

$song_list = $xml->getElementsByTagName('songs');
$song_node = $xml->createElement('song');
$song_node->setAttribute('display','Third Song');
$song_node->setAttribute('url', '3.mp3');

$song_list->appendChild($song_node);

?>

Perfect.

Now how do I edit existing song nodes?

Once you have your $song_list

$song_nodes = $song_list->getElementsByTagName('song');
foreach ($song_nodes AS $song) {
  $song->setAttribute('display', 'New Display');
}

The easiest way to determine which node you're on would be to do a
$song->getAttribute('display')  inside of the foreach and do an "If" on it

I'm applying your first comment. The xml file is at ../music/songList.xml

What am I doing wrong (I'm inserting a new node):

 <?php
include('includeme.php');
if(isset($_POST['submit']))
{
$xml = new DOMDocument;
$xml->loadXML($../music/song_xml); /*where song_xml is the xml you provided*/
$song_list = $xml->getElementsByTagName('songs');
$song_node = $xml->createElement('song');
$song_node->setAttribute('display',$_POST['display']);
$song_node->setAttribute('url', $_POST['url']);
$song_list->appendChild($song_node);
}
?>

Since it's a file that you're loading and not a string (I should have asked), you want to do

$xml->load('../music/songList.xml');

and then the rest.

Great. I'm new at XML and not that great with php, so I will apply your suggestions and get back to you if I run into trouble.

Thanks!

no problem.  good luck!

OK. I know it's something I'm overlooking, but I'm getting this:

Warning: domdocument() expects at least 1 parameter, 0 given in /homepages/31/d143768754/htdocs/rod_music2/admin/add-music-page1.php on line 5

Fatal error: Call to undefined method: domdocument->load() in /homepages/31/d143768754/htdocs/rod_music2/admin/add-music-page1.php on line 6

code: www.own-designs.com/rod_music2/admin/add-music-page1.txt   

ahh... try

$xml = new DOMDocument();

add the parenthesis

Made the change, still getting these errors:


Warning: domdocument() expects at least 1 parameter, 0 given in /homepages/31/d143768754/htdocs/rod_music2/admin/add-music-page1.php on line 5

Fatal error: Call to undefined method: domdocument->load() in /homepages/31/d143768754/htdocs/rod_music2/admin/add-music-page1.php on line 6

Hmm,
  Make sure that you have the DOM extension installed for PHP.  That's the only guess I have.

I'm on a shared hosting package.

I'll run phpinfo

Looks OK:

http://own-designs.com/rod_music2/phpinfo1.php

perhaps we should use a MySQL database

Oh php4... that might be causing it as well.

you'll have to use DOMXML instead of just DOM
http://us.php.net/manual/en/ref.domxml.php

TRY:

$xml = domxml_open_file("../music/songList.xml");
$song_list = $xml->get_elements_by_tag_name('songs');
$song_node = $xml->create_element('song');
$song_node->set_attribute('display',$_POST['display']);
$song_node->set_attribute('url', $_POST['url']);
$song_list->append_child($song_node);

Now I'm getting this error:

Fatal error: Call to undefined method: domdocument->get_elements_by_tag_name() in /homepages/31/d143768754/htdocs/rod_music2/admin/add-music-page1.php on line 6

I'm going a different route.
I'm using:

<?
$doc = new_xmldoc('1.0');
$root = $doc->add_root('songs');
$member = $root->new_child('song','display');
$fp = @fopen('members.xml','w');
if(!$fp) {
    die('Error cannot create XML file');
}
fwrite($fp,$doc->dumpmem());
fclose($fp);
?>

which works except for my <song> tags need to read

<song display="string1" url="string2" />

I think I can do it all if you help me with this

Thanks!

Got it.
That works.

Let me apply this and return.

Works great!