public static function getChangeSubscriptionXml($timeframe, $newPlanCode, $newQuantity, $newUnitAmount, $add_ons)
{
$doc = new DOMDocument("1.0");
$root = $doc->appendChild($doc->createElement("subscription"));
$root->appendChild($doc->createElement("timeframe", $timeframe));
if ($newPlanCode != null) {
$root->appendChild($doc->createElement("plan_code", $newPlanCode));
}
if ($newQuantity != null) {
$root->appendChild($doc->createElement("quantity", $newQuantity));
}
if ($newUnitAmount != null) {
$root->appendChild($doc->createElement("unit_amount", $newUnitAmount));
}
if (isset($add_ons)) {
$root->appendChild(RecurlySubscription::getAddOnsXml($add_ons, $doc));
}
return $doc->saveXML();
}
