$padd = '    '; //4 spaces for identation
$eol = "n"; //end of line
$xml = '<?xml version="1.0"?>'.$eol;
$xml .= '<products>'.$eol;
foreach ($collection as $product) {
    $xml .= $padd.'<product>'.$eol;
    $xml .= str_repeat($padd, 2).'<name>'.$product->getName().'</name>'.$eol;
    $xml .= str_repeat($padd, 2).'<description><![CDATA['.$product->getName().']]></description>'.$eol;
    $xml .= str_repeat($padd, 2).'<price><![CDATA['.$product->getFinalPrice().']]></price>'.$eol;
    //add here all the attributes you need to export
    $xml .= $padd.'</product>'.$eol;
}
$xml .= '</products>'.$eol;
//Do something with $xml - save it in a file or echo it.