xml2xml

<?php

if (!@$_POST['xml'])
{
    ?>Текст исходного XML:
    <form action="<?=$_SERVER['REQUEST_URI']?>" method="post">
        <textarea name="xml" rows="30" cols="90"/></textarea><br>
        <input type="submit" value="Конвертировать"/>
    </form>
    <?php die();
}

function appendChild(DOMElement $root, $name, $value = null)
{
    $el = $root->ownerDocument->createElement($name);
    $value ? $el->nodeValue = $value : null;
    return $root->appendChild($el);
}

$inXml = new DOMDocument();
$inXml->preserveWhiteSpace = false;
$inXml->loadXML($_POST['xml']);

$outXml = new DOMDocument('1.0', 'UTF-8');
$outXml->preserveWhiteSpace = false;
$outXml->formatOutput = true;

$outChildren = $outXml->appendChild($outXml->createElement('children'));

foreach ($inXml->documentElement->childNodes as $oldChild)
{
    $oldChild = simplexml_import_dom($oldChild);
    $newChild = appendChild($outChildren, 'child');

    $name = appendChild($newChild, 'name');
    appendChild($name, 'last', $oldChild->ТЕКСТ7);
    appendChild($name, 'first', $oldChild->ТЕКСТ8);
    appendChild($name, 'middle', $oldChild->ТЕКСТ9);

    $dateOfBirth = strtotime($oldChild->ТЕКСТ11);
    $dateOfBirth = date('Y-m-d', $dateOfBirth) . 'Z';

    appendChild($newChild, 'dateOfBirth', $dateOfBirth);
    appendChild($newChild, 'polisSer', $oldChild->ТЕКСТ24);
    appendChild($newChild, 'polisNum', $oldChild->ТЕКСТ27);
    appendChild($newChild, 'documentSer', $oldChild->ТЕКСТ61);
    appendChild($newChild, 'documentNum', $oldChild->ТЕКСТ56);
    appendChild($newChild, 'mkb', 'Z00');
}

$outData = $outXml->saveXML();
header('Content-Length:' . strlen($outData));
header("Content-Type: application/octet-stream");
header("Content-Disposition: attachment;filename=\"out.xml\"");
echo $outData;