index.php
---------
<?php
header('Content-type: application/xml; charset="utf-8"');

require_once 'Smarty.class.php';

$plk = file('owoce.txt');
$s = new Smarty;
$s->assign('owoce', $plk);
$s->display('owoce.tpl');
?>


owoce.tpl
---------
<?xml version="1.0" encoding="utf-8"?>
<owoce>
{section name=i loop=$owoce}
    <owoc>{$owoce[i]|trim}</owoc>
{/section}
</owoce>