<?php

// Start XML file, create parent node
$xml = new XMLWriter();
$xml->openMemory(); // create document in memory (AKA storing into a var)
$xml->setIndent(true); // autoindent output
$xml->setIndentString(' '); // set kind of indentation

$xml->startDocument('1.0','UTF-8'); // start xml declaration with encoding utf-8

$xml->startElement("markers");

foreach( $dbMarkers as $m )
{
    $xml->startElement("marker");
        $xml->writeAttribute("photo", $m['img'] );
        $xml->writeAttribute("name",  $m['name'] );
        $xml->writeAttribute("lng",   $m['lng']);
        $xml->writeAttribute("lat",   $m['lat']);
    $xml->endElement();
}

$xml->endElement();
echo $xml->outputMemory(false);