PHP Copy Node from Source XML File to Parent XML File with Matching Attribute ID

First post, so please be kind. :) I've been struggling with this for days. I have three XML files with related content and have already conquered the first two. The first two were simple 1)LOTDATA.XML - Contains Data for a specific Dealer by DealerID and 2) vehicles.xml, which contains a list of inventory with child attributes for all Dealers in File#1, again, by DealerID. I iterate through the first file and output an XML for each Dealer with the file name $dealerid.xml. I then iterate through the vehicles.xml file and sequentially place each Vehicle into its corresponding Dealer File by DealerID. Here's where it gets fun; the Third File, LINKS.XML, contains data for each of the Vehicles in File#2 by both DealerID and VIN (Unique ID). What I need to do is get each Links Node appended as a child of the corresponding VIN in its related $dealerid.xml file. I've tried XML Path and all sorts of variations with no joy. The closest I have come is to iterate through all the Links and ECHO its matched VIN in the dealerid.xml file. However, when I try to go through the steps to append a child to the related record, the closest I come is that it adds EVERY Links Node that matches the current DealerID to the first Vehicle Record in the parent file. Following is the closest working code I have come up with:

// Get the DealerID of the Record, and Add Node to the corresponding DealerID.xml file

$linksinfo = 'LINKS.XML';

$links = new xmlReader();

$links->open($linksinfo);

$linksnode = 'LINKS';

while($links->read() && $links->name !== $linksnode);

set_time_limit (180);

// Move to the first vehicle

while($links->name === $linksnode) {

    // let's get this Links Node into a SimpleXMLElement

    $mylinks = new SimpleXMLElement($links->readOuterXML());

    // Get the DealerID for Parent File Name

    $localdealerid = $mylinks->DealerID;

    // Identify the parent file

    $parentfile = "$localdealerid.xml";

    //Pull the VIN Number for reference

    $localvinnumber = $mylinks->VIN;

  $parentdoc = new DOMDocument();

  $parentdoc->formatOutput = true;

  $parentdoc->preserveWhitespace = false;

  $parentdoc->load($parentfile, 0) or die ("Couldnt Open Parent Doc");

    echo "Opened Dealer File";
  $childdoc = dom_import_simplexml($mylinks) or die ("Error Opening Links File");

  $childdoc->formatOutput = true;

  $childdoc->preserveWhitespace = false;

     echo "Opened Links File <br>";

     echo "Local Dealer ID is $mylinks->DealerID <br>";

     echo "Searching to match VIN $localvinnumber <br>";
    $inventory = $parentdoc->getElementsByTagName('VIN');
   foreach($inventory as $vehicle){
            $vehicleid = $vehicle->nodeValue or die ("Error Iterating Inventory");
            if($vehicleid = $localvinnumber ){
                $root = $parentdoc->getElementsByTagName('VEHICLES')->item(0) or die ("Error Getting Matching VIN");
                echo "Matched to $vehicleid  <br>";
                $xmlcontent = $parentdoc->importnode($childdoc,true);
                $root->appendChild($xmlcontent) or die ("Error Appending Child Record");
                $parentdoc->save($parentfile) or die ("Error Saving Parent File");
                echo "Success! <br>";                   
                break; // Moves Iteration to next Links Node
            } else {
                // do nothing
                }
           break;               
    }

// Move to next Linkset

$links->next($linksnode) ;

}