$doc = new DOMDocument('1.0', 'UTF-8');
$xns = 'http://www.w3.org/2000/xmlns/';
$mns = 'http://example.com/aBc/2/';
$ons = 'http://example.com/test/2005/something';
$ns =  'http://example.com/main/';

$firstChild = $doc->createElement('firstChild');
$firstChild->setAttributeNS($xns, 'xmlns:cns1', $mns);
$firstChild->setAttributeNS($xns, 'xmlns:i', $ons);

$elements = $doc->createElementNS($mns, 'cns1:elements');

for($i = 0; $i < 3; $i++) {
    $e = $doc->createElementNS($mns, 'cns1:element');
    for($k = 0; $k < 2; $k++) {
        $r = rand(100, 999);
        $value = round(($r*rand(1,9))/rand(1,9), 2);
        $ce = $doc->createElementNS($mns, "cns1:elementValue$r", $value);
        $e->appendChild($ce);
    }
    $elements->appendChild($e);
}
$firstChild->appendChild($elements);

$otherTag = $doc->createElementNS($mns, 'cns1:otherTag', 'some_value');
$emptyTag = $doc->createElementNS($mns, 'cns1:emptyTag');
$emptyTag->setAttributeNS($ons, 'i:nil', 'true');

$firstChild->appendChild($otherTag);
$firstChild->appendChild($emptyTag);

$main = $doc->createElementNS($ns, 'main');
$main->appendChild($firstChild);

$doc->appendChild($main);


header('Content-Type: text/xml');

echo $doc->saveXML();