$url = "http://192.168.31.50:3000/pay";

$data = [
 "amount" => 250
];

$options = [
 "http" => [
  "header" => "Content-Type: application/json",
  "method" => "POST",
  "content" => json_encode($data)
 ]
];

$context = stream_context_create($options);

$result = file_get_contents($url, false, $context);

echo $result;