I am trying to add a product in php, all in xml, here is what I have already done:

        $file = file_get_contents('php://input');
        $xml = simplexml_load_file($file);

        $product = new Product($xml->id);
        $dom = new DOMDocument;

        $xml->id = $product->id = "29";
        $xml->name = $product->name = "Baptiste";
        $xml->price = $product->price = "90";
        $xml->description = $product->description = "loricup Ilicum Bababcom OEGZJpodbnsoqdqsfkjifhum";

        $id = $dom->createElement('id', "$xml->id");
        $name = $dom->createElement('name', "$xml->name");
        $price = $dom->createElement('price', "$xml->price");
        $description = $dom->createElement('description', "$xml->description");

        $dom->appendChild($id);
        $dom->appendChild($name);
        $dom->appendChild($price);
        $dom->appendChild($description);

        $dom->formatOutput = true;
        $this->output .= $dom->saveXML();

This is why I am appealing to you to try to help me!

thank you in advance for your help