XML node append child called in a loop

In this php function I append to the node by calling that function in a loop through ajax. The first time the call to appen开发者_Go百科child succeeds. The second time there is a php error "call to undefined method". I don't understand why this happens.

Here is the php function

<?php

ini_set('display_errors', 1);
error_reporting(E_ALL);

function mysql_escape_mimic($inp) { 
    if(is_array($inp)) 
        return array_map(__METHOD__, $inp); 

    if(!empty($inp) && is_string($inp)) { 
        return str_replace(array('\\', "\0", "\n", "\r", "'", '"', "\x1a"), array('\\\\', '\\0', '\\n', '\\r', "\\'", '\\"', '\\Z'), $inp); 
    } 

    return $inp; 
}


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);
   }

   $xurl = $dom->createElement("URL"); 
   $xurl->setAttribute("ID", $urlid);
   $xurls->appendChild($xurl);  /*  Function fails here second time, when node exists already */

   $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); 

}
   echo "from add_url urlid: ".$urlid." urlname ".$urlname." urllink ".$urllink;
$dom->save('communities.xml');
}

echo add_url(trim($_REQUEST['nodeid']), trim($_REQUEST['urlid']), trim($_REQUEST['urlname']), trim($_REQUEST['urllink']));

?>

Here is the XML structure.

<?xml version="1.0" encoding="ISO-8859-1"?>
<COMMUNITIES>
  <COMMUNITY ID="c000002">   
  <NAME>ID000002</NAME>
  <TOP>192</TOP>
  <LEFT>297</LEFT>
  <WIDTH>150</WIDTH>
  <HEIGHT>150</HEIGHT>
  <URLS>
    <URL ID="u000002">
       <NAME>Facebook.com</NAME>
       <URLC>http://www.facebook.com</URLC>
    </URL>
   </URLS>
  </COMMUNITY>
</COMMUNITIES>

---

Try editing like this:

...
if ($xurls->length) {
    $xurls = $xurls->item(0); // from DOMNodeList to DOMNode

This is because later you're appending a child to $xurls, so it must be an element (such as the one returned by createElement()) instead of a list, like PHP says:

Fatal error: Call to undefined method DOMNodeList::appendChild()