gistfile1.txt

<?php
	
	$dst = simplexml_load_file( '35928_3210820_mp.xml' );
	$dst = dom_import_simplexml( $dst )->ownerDocument;
	$parent = $dst->getElementsByTagName( 'merchandiser' )->item(0);
	
	$src = simplexml_load_file( '39153_3210820_mp.xml' );
	
	foreach( $src->product as $product )
  {
      var_dump($src);
      $node = dom_import_simplexml( $product );
      $node = $dst->importNode( $node, 1 );
      $parent->appendChild( $node );
  }

	$final = new DOMDocument();
	$final->loadXML( $dst->saveXML(), LIBXML_NOBLANKS );
	$final->formatOutput = True;
	echo $final->saveXML();

?>