How to send an XML response (POST) to another server?

Question

PHP

Good day, comrades. I am engaged in the integration of Ya.Money, namely Ya.Kassa. Some problems have arisen. TP is silent, the time is late. What is the essence of the problem: I
connected the form, the amount is formed correctly, but when paying for the order already in the service, error 0023 is returned. I understand that the order does not pass the check(checkOrder) on the side of my store.
The manual says that you need to send a response to check the order in the form of XML. How can you send it? And which URL exactly?
Though, an essence of a question in formation of XML of the answer.
Thank you.

Answer 1

$xml = '<?xml version="1.0" encoding="UTF-8"?>
      <checkOrderResponse performedDatetime ="' . date( 'c' ) . '" code="' . $code . '" invoiceId="' . $post['invoiceId'] . '" shopId="' . $post['shopId'] . '"/>';
      header( 'Content-type:application/xml;' );
      echo $xml;

you do not need to send a response, but Yandex will take it.