Accept POST data in JSON format

post.php

<?php

$response = (object) [];
$json = json_decode(file_get_contents('php://input'));

//...

if (!$json) {
  $response->state = [
    'code' => 400,
    'type' => 'error',
    'message' => 'Something went wrong. Please try again'
  ];

  http_response_code($response->state['code']);
  echo json_encode($response);
  exit;
}

//...

$response->state = [
  'code' => 200,
  'type' => 'success',
  'message' => 'Thank you for your submission',
];

http_response_code($response->state['code']);
echo json_encode($response);
exit;