Question

I have this PHP code that adds a set of nodes to an XML file. It does most of what it should do, it finds where to make the additions, but then it doesn’t make the update.

I have an xml file of this structure.

<COMMUNITIES>
  <COMMUNITY ID="c001">
       <URLS>
           <URL ID="u001">
              <NAME>Google.com</NAME>
              <URL>http://www.google.com</URL>
           </URL>
       </URLS>
  </COMMUNITY>
</COMMUNITIES>

The updates are being made to the URLS node. The user clicks an “Add URL” link and I add the new URL to this node like this.

       <URL ID="u002">
          <NAME>Yahoo.com</NAME>
          <URL>http://www.yahoo.com</URL>
       </URL>

If the URLS node exists, I append the new url node. If the URLS node does not exist, I create it, then append the new url node.

There are no errors, everything seems to work, but the URLS node is empty. Here is the PHP script.

function add_url( $nodeid, $urlid, $urlname, $urllink ) {

$dom = new DOMDocument();
$dom->load('communities.xml');

$dom->formatOutput = true; 
$dom->preserveWhiteSpace = false;

// get document element  

$xpath = new DOMXPath($dom);
$nodes = $xpath->query("//COMMUNITY[@ID='$nodeid']"); 

if ($nodes->length) {
   $node = $nodes->item(0); 

   $xurl = $dom->createElement("URL"); 
   $xurl->setAttribute("ID", $urlid);

   $xuname     = $dom->createElement("NAME");  
   $xunameText = $dom->createTextNode(mysql_escape_mimic($urlname));  
   $xuname->appendChild($xunameText); 

   $xulink     = $dom->createElement("URL");  
   $xulinkText = $dom->createTextNode(mysql_escape_mimic($urllink));  
   $xulink->appendChild($xulinkText); 

   $xurl->appendChild($xuname); 
   $xurl->appendChild($xulink); 

   $xurls = $xpath->query("//COMMUNITY[@ID='$nodeid']/URLS");

   if ($xurls->length) {
   }
   else {
      $xurls = $dom->createElement("URLS"); 
   }

   $xurls->appendChild($xurl);

   /* $node->appendChild($xurls); */

}

$dom->save('communities.xml');
}

I thought the problem was that I was appending the URLS node when it already existed. But I commented out that line. I am sure the problem is simple, but I am new at this. I looked on the site and did not find that specific situation.

Edit

1. Removed return statement before if ($xurls->length).

2. Fixed function.

Answer 1

The problem was that I was attempting to add nodes to a node which was already in the XML file as empty.

Instead of the node having data like this.

<URLS>
   <URL ID="u001">
      <NAME>Google.com</NAME>
   </URL>
</URLS>

I had a node like this.

<URLS/>

Common sense says that this should not be a problem. If the node is empty then appendChild should just add the data and rewrite the node as.

<URLS>
   <URL ID="u002">
      <NAME>Yahoo.com</NAME>
   </URL>
</URLS>

Here is the PHP script that worked. You will note that I created a new node instead of appending to <URLS/>. I also reordered the appendChild to start from the top node instead of the creating the child nodes first then appending a set of nodes to the top node.

function add_url( $nodeid, $urlid, $urlname, $urllink ) {

$dom = new DOMDocument();
$dom->load('communities.xml');

$dom->formatOutput = true; 
$dom->preserveWhiteSpace = true;

// get document element  

$xpath = new DOMXPath($dom);
$nodes = $xpath->query("//COMMUNITY[@ID='$nodeid']"); 

if ($nodes->length) {

   $node = $nodes->item(0); 

   $xurls = $xpath->query("//COMMUNITY[@ID='$nodeid']/URLS");


   if ($xurls->length) {
   }
   else {
      $xurls = $dom->createElement("URLS"); 
      $node->appendChild($xurls);
   }

      $xurls = $dom->createElement("URLSC"); 
      $node->appendChild($xurls);

   $xurl = $dom->createElement("URL"); 
   $xurl->setAttribute("ID", $urlid);
   $xurls->appendChild($xurl);

   $xuname     = $dom->createElement("NAME");  
   $xunameText = $dom->createTextNode(mysql_escape_mimic($urlname));  
   $xuname->appendChild($xunameText); 
   $xurl->appendChild($xuname); 

   $xulink     = $dom->createElement("URLC");  
   $xulinkText = $dom->createTextNode(mysql_escape_mimic($urllink));  
   $xulink->appendChild($xulinkText); 
   $xurl->appendChild($xulink); 

}

$dom->save('communities.xml');
}

So I must modify the function that creates the empty node <URLS/>. I should not create the node in that function but create it here in the add_url function only when it doesn’t exist.