XML transformation using PHP5 DOM
<?xml version='1.0' encoding='ISO-8859-1'?>
<!DOCTYPE words SYSTEM "words.dtd">
<words>
<word id="word_1">Alfa</word>
<word id="word_2">Beta</word>
<word id="word_3">Gamma</word>
<word id="word_4">Delta</word>
<word id="word_5">Zeta</word>
</words>

word_1 = Alfa

<?php

$xmlHitzakDok = new DOMDocument();

if($xmlHitzakDok->load("words.xml") === FALSE){die('Errorea hitzen xml-a kargatzean');}

$xPath_Hitzak = new DOMXPath($xmlHitzakDok);

$Hurrengo_Hitza = 'word_1';

foreach ($xPath->query('//words/word') AS $item)
{
   if ($item->getAttribute('id') == $Hurrengo_Hitza)
   {
    echo $item->getAttribute('id') . " = " . $item->nodeValue . "<br />";
   }
}