Как отправит Json через php на Api ПриватБанка ( Оплата частями )?

$password = "75bef16bfdce4d0e9c0ad5a19b9940df";
$storeId = "4AAD1369CF734B64B70F";
$orderId = 555656565;
$amount = 400.00;
$partsCount = 6;
$merchantType = "PP";
$responseUrl = "http://shop.com/response";
$redirectUrl = "http://shop.com/redirect";
$products_string = "Микроволновка";
$signature = base64_encode(sha1($password.$storeId.$orderId.$amount.$partsCount.$merchantType.$responseUrl.$redirectUrl.$products_string.$password, true ));
// $json=json_encode($signature);
$ch = curl_init('https://payparts2.privatbank.ua/ipp/v2/payment/create.json'); 
curl_setopt($ch,CURLOPT_POSTFIELDS,$data);
curl_setopt($ch,CURLOPT_PROTOCOLS,CURLPROTO_HTTPS);
curl_setopt($ch,CURLOPT_HTTP_VERSION,CURL_HTTP_VERSION_1_1);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST,'POST');
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));
curl_setopt($ch, CURLOPT_POSTFIELDS, $signature);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
 $result = curl_exec($ch);
 curl_close($ch);
$result_private = json_decode($result, 1);
 print_r ($result_private);