// Call the Funktion sign($jsonData, $secret) in CreateProductJsonOrderwithSignature.php with parameters $jsonData and
// secret:
$jsonData = '{"totalprice":"17.97","callbackurl":"https://www.anbietershop.de/HandleonOfficeOrderResponse.php","parametercacheid":"0e81f10f-6de8-4edc-cdcf-de96cf61624c","products":[{"quantity":"3","circleofusers":"customer","price":"5.99","name":"onOffice Sample 1"}]}'
$secret = 'myTestSecret'

// Add timestamp (in this example 1565689180);
$jsonDecodedContent = json_decode($jsonData, true);
$jsonDecodedContent['timestamp'] = time();

// sorted array after call of sortParameters($jsonDecodedContent):
[
  "callbackurl" => "https://www.anbietershop.de/HandleonOfficeOrderResponse.php",
  "parametercacheid" => "0e81f10f-6de8-4edc-cdcf-de96cf61624c",
  "products" => [
      [
        "circleofusers" => "customer",
        "name" => "onOffice Sample 1",
        "price" => "5.99",
        "quantity" => "3"
     ]
   ],
  "timestamp" => 1565689180,
  "totalprice" => "17.97"
]

// The string to be signed loos like this (after call of http_build_query($jsonContent, '', '&', PHP_QUERY_RFC3986)):
callbackurl=https%3A%2F%2Fwww.anbietershop.de%2FHandleonOfficeOrderResponse.php&parametercacheid=0e81f10f-6de8-4edc-cdcf-de96cf61624c&products%5B0%5D%5Bcircleofusers%5D=customer&products%5B0%5D%5Bname%5D=onOffice%20Sample%201&products%5B0%5D%5Bprice%5D=5.99&products%5B0%5D%5Bquantity%5D=3&timestamp=1565689180&totalprice=17.97

// Generate following signature with secret "myTestSecret" and call of 
// $jsonSignature = hash_hmac('sha256', $jsonQueryContent, $secret):
49b818db62d1b86640ea34f4525e64809fa44d5e0b90ad719aadd5425f66c9ba