Conflict of two JSONs or why this error?

Question

AJAX

Hello.
The usual form where you need to perform an action upon successful completion of ReCaptcha and display a message about successful submission or error. But apparently there is a JSON conflict,

Error:

syntax error unexpected token in json at position 0

I think the error is that there are two different JSON requests, because without adding the code from ReCaptcha, everything works fine with the current JSON without ReCaptcha.
Tell me how to solve this?!

<script> 
    $(document).ready(function() { 
      $("#feedback").submit(function(){ 
        var form = $(this); 
        var error = false; 
        form.find('input, textarea').each( function(){ 
          if ($(this).val() == '') { 
            alert('Зaпoлнитe пoлe "'+$(this).attr('placeholder')+'"!');
            error = true; 
          }
        });
        if (!error) { 
          var data = form.serialize(); 
          $.ajax({ 
            type: 'POST', 
            url: 'send.php', 
            dataType: 'json', 
            data: data,
            beforeSend: function(data) { 
              form.find('input[type="submit"]').attr('disabled', 'disabled'); 
            },
            success: function(data){ 
              if (data['error']) { 
                alert(data['error']);
              } else { 
                alert('Письмo было отправлено, проверьте почту.');
              }
            },
            error: function (xhr, ajaxOptions, thrownError) { 
              alert(xhr.status); 
              alert(thrownError);
            },
            complete: function(data) {
              form.find('input[type="submit"]').prop('disabled', false); 
            }
                          
               });
        }
        return false; // вырубaeм стaндaртную oтпрaвку фoрмы
      });
    });
  </script>

<?php
if ($_POST) { 
  
  // ReCaptcha Start
  $secret = 'здесь мой секретный ключ от reCapctha';
  $ip = $_SERVER['REMOTE_ADDR'];

  $response = $_POST['g-recaptcha-response'];

  $rsp = file_get_contents("https://www.google.com/recaptcha/api/siteverify?secret=$secret&response=$response&remoteip=$ip");

  $arr = json_decode($rsp, TRUE);

  if($arr['success']){ 	// ReCaptcha проверка на успех ...
      $author = $_POST['author'];
      $author = addslashes($author);
      $author = htmlspecialchars($author);
      $author = stripslashes($author);
      $author = mysql_real_escape_string($author);
      
      $message = $_POST['message'];
      $message = addslashes($message);
      $message = htmlspecialchars($message);
      $message = stripslashes($message);
      $message = mysql_real_escape_string($message);

      $date = date("d-m-Y в H:i:s");
      $result = mysql_query("INSERT INTO messages (author, message, date) VALUES ('$author', '$message', '$date')");
  }
  // Обработка ошибок и вывод
  $json = array(); 
  if (!$name or !$author or !$message) { 
    $json['error'] = 'Вы зaпoлнили нe всe пoля.'; 
    echo json_encode($json); 
    die();
  }

  $json['error'] = 0;

  echo json_encode($json); 
} else { 
  echo 'У вас нет прав для входа на эту страницу!'; 
}
?>