<?php
$url = 'http://hebbohotel.com.br/swf/gordon/RELEASE-HEBBO/effectmap.xml';

$ch = curl_init();

curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_BINARYTRANSFER, 1); //Transferencia binaria
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); //Força retornar transferência na variavel

$xml = gzdecode(curl_exec($ch));

curl_close($ch);

$dom = new DOMDocument;
$dom->loadXML($xml);
$effects = iterator_to_array($dom->getElementsByTagName('effect'));//Passa para array

//-3 no segundo parametro pega os 3 ultimos itens
$effects = array_slice($effects, -3);

foreach ($effects as $effect) {
    echo $effect->getAttribute('id'), PHP_EOL;
}