使用php xml生成特定格式

Hi i want to create a php code which generates xml of specific format given below. Kindly help me through this

<?xml version="1.0" encoding="utf-8"?>
<order>
    <requisition>
        <dateofservice>2012-12-13</dateofservice>
        <labid>str1234</labid>
        <reqnotes_c>str1234</reqnotes_c>
        <rptemail_c>str1234</rptemail_c>
        <rptmethod_c>str1234</rptmethod_c>
        <specimen_type_c>str1234</specimen_type_c>
        <collectiontype_c>str1234</collectiontype_c>
    </requisition>
    <patient>
        <firstname>str1234</firstname>
        <lastname>str1234</lastname>
        <dob>2012-12-13</dob>
        <breed_c>str1234</breed_c>
        <species>str1234</species>
        <sex>s</sex>
        <sterilization_c>str1234</sterilization_c>
    </patient>
</order>

My code is this Now correct me please. My code gives only one parent and i want to generate the output as given above

while (($row = fgetcsv($inputFile)) !== FALSE){
    $container = $doc->createElement('row');
    foreach($headers as $i => $header) {
        if(!empty($row[$i])) {
            $child = $doc->createElement($header);
            $child = $container->appendChild($child);
            $value = $doc->createTextNode($row[$i]);
            $value = $child->appendChild($value);
        }
    }
    $root->appendChild($container);
}
$strxml = $doc->saveXML();