PHP XML DOM Uncaught exception 'DOMException' with message 'Wrong Document Error' - php

Question

I am trying to learn XML and I know this is a problem with not properly importing the Nodes. But I can't quite figure it out. I've been looking around and most people don't have multiple child elements like I do with the departments.
Here is my XML structure:
<SOT>
<DEPARTMENT name="Aviation Technology" id="AT">
<EMPLOYEE type="Faculty">
<LOGIN>jdoe1</LOGIN>
<NAME>John Doe</NAME>
</EMPLOYEE>
<EMPLOYEE type="Faculty">
<LOGIN>jdoe2</LOGIN>
<NAME>Jane Doe</NAME>
</EMPLOYEE>
<EMPLOYEE type="Faculty">
<LOGIN>jdoe3</LOGIN>
<NAME>Joe Doe</NAME>
</EMPLOYEE>
</DEPARTMENT>
<DEPARTMENT name="Building and Construction Management" id="BCM">
</DEPARTMENT>
<DEPARTMENT name="Computer Graphics Technology" id="CGT">
</DEPARTMENT>
</SOT>
I understand that SOT is my root element and that departments are "children" of SOT and each department has multiple employee "children". The problem I run into is when I am trying to add a new employee to a certain department. When I try $departmentArray->item($i)->appendChild($employee); I get the Wrong Document Error.
I'm using this PHP code to try and append the child to the departmentNode
<?php
//grab form data
$username = $_POST['username'];
$employeeName = $_POST['employeeName'];
$department = $_POST['department'];
//create new DOMDocument to hold current XML data
$doc = new DOMDocument();
$doc->load("test.xml");
$xpath = new DOMXpath($doc);
//create our new DOMDocument for combining the XML data
$newDoc = new DOMDocument();
$newDoc->preserveWhiteSpace = false;
//create School of Tech Node and append to new doc
$sotElement = $newDoc->createElement("SOT");
$newDoc->appendChild($sotElement);
$root = $newDoc->documentElement;
//grab the department Nodes
$departmentArray = $doc->getElementsByTagName("DEPARTMENT");
//create a new employee and set attribute to faculty
$employee = $newDoc->createElement("EMPLOYEE");
$employee->setAttribute("type", "Faculty");
//counters (might use them later for ->item(counter) function
$indexCounter = 0;
$i = 0;
foreach($departmentArray as $departmentNode){
if(strcmp($departmentNode->getAttribute('name'),$department) == 0){//check if departments match
//create login element
$loginNode = $newDoc->createElement("LOGIN");
$loginNode->appendChild($newDoc->createTextNode($username));
$employee->appendChild($loginNode);
//create name node
$nameNode = $newDoc->createElement("NAME");
$nameNode->appendChild($newDoc->createTextNode($employeeName));
$employee->appendChild($nameNode);
//append employee onto department node
//$departmentArray->item($i) = $doc->importNode($departmentArray->item($i), true);
$departmentArray->item($i)->appendChild($employee);
//set index of department array (possibly used for appending later)
$indexCounter = $i;
}
$i++;
}
#######################################
/*Write out data to XML file */
#######################################
//$departmentArray = $doc->getElementsByTagName("DEPARTMENT");
foreach($departmentArray as $departmentNode){
$tempNode = $newDoc->importNode($departmentNode, true);
/*if(strcmp($departmentNode->getAttribute('name'),$department) == 0){
$sotElement->appendChild($employee);
}*/
$sotElement->appendChild($tempNode);
}
$newDoc->formatOutput = true;
$newDoc->save("test2.xml");
?>
Any help explaining how to properly import all the department nodes to be able to append onto them would be greatly appreciated. I've tried using arrays.

Answer 1

You need to import any node to append it to another document:
$departmentArray->item($i)->appendChild( $doc->importNode( $employee, true ) );

Answer 2

I'm pretty sure that this is happening because you are trying to append an element from a different document into your output document.
I found this code in a comment on php's site for DOMNode::cloneNode which might be what you want.
<?php
$dom1->documentElement->appendChild(
$dom1->importNode( $dom2->documentElement, true )
);
?>
Alternatively, you could look at exporting the node's XML and reimporting it into a DOMDocumentFragment, but I'd have to experiment to know for sure.