Something

$dom = new domDocument("1.0","ISO-8859-1");
$dom->formatOutput = 1;
$root = $dom->createElement('forum');
$branch = $dom->createElement('post');
	$leaf = $dom->createElement('title');
	$leaf = appendChild($dom->createTextNode('First Post!!!'));
	$branch->appendChild($leaf);

	$leaf = $dom->createElement('link');
	$leaf = appendChild($dom->createTextNode('http://fudforum.org/index.php/m/1'));
	$branch->appendChild($leaf);

	$leaf = $dom->createElement('description');
	$leaf = appendChild($dom->createTextNode('1st message in the forum.'));
	$branch->appendChild($leaf);

$root->appendChild($branch);
$dom->appendChild($root);
echo $dom->saveXML;