How to change status with AJAX?

I will not be able to help with the PHP part, but I will try to give an orientation when the AJAX request.

First, try putting all the inputs that you plan to receive on the server within form

Let's take as an example the following mark-up html .:

<form id="formulario" action="atualiza.php" method="POST">
  <div>
    <label>
      Autor:
      <input id="Author" name="Author" type="text" />
    </label>
  </div>
  <div>
    <label>
      Data Referencia:
      <input id="DataReferencia" name="DataReferencia" type="text" />
    </label>
  </div>
  <div>
      <label>
      Registos 01:
      <input id="Registos_1" name="Registos[]" type="text" />
    </label>
  </div>
  <div>
      <label>
      Registos 02:
      <input id="Registos_2" name="Registos[]" type="text" />
    </label>
  </div>
  <div>
      <label>
      Registos 03:
      <input id="Registos_3" name="Registos[]" type="text" />
    </label>
  </div>
  <div>
    <input id="Enviar" type="submit" value="Value" />
  </div>
</form>

I think you're familiar with the code above, and you know how to retrieve the Autor , DataReferencia , and Registos[] fields when they reach your server.

The way you will recover the data on the server will not change, what will change is how to send the data and retrieve the same.

For this, I advise you to manipulate the event submit of form#formulario

var formulario = document.getElementById("formulario");
formulario.addEventListener("submit", function (event) {
  // cancelando o envio sincrono do formulario.
  event.preventDefault();

  var data = new FormData(formulario);
  var httpRequest = new XMLHttpRequest(formulario.method, formulario.action, true);
  httpRequest.open();
  httpRequest.addEventListener("readystatechange", function (event) {
    if (httpRequest.readyState == 4) {
      if (httpRequest.status == 200) {
        // a requisição ajax deu certo
        console.log(httpRequest.response);
      } else {
        // ocorreu um erro durante a requisição AJAX.
        console.error(httpRequest.statusText);
      }
    }
  });
  httpRequest.send(data);
});

In your code PHP you have two options, return a string with a HTML already mounted and replace the HTML of the page, or return a JSON object and use it to manipulate your page .

In both cases, you will need to set a responseType property of your httpRequest and handle the return as follows:

Text / HTML

// antes de enviar
httpRequest.responseType = "text";

// ao receber a resposta com sucesso.:
// limpando o DOM que vai receber o novo conteudo.
var destino = document.getElementById("destino");
while (destino.firstChild) {
  destino.removeChild(destino.firstChild);
}  

// montando o novo conteudo.
var parser = new DOMParser();
var node = parser.parseFromString(xmlHttp.responseText, "text/html");
destino.appendChild(node.documentElement);

JSON

// antes de enviar
httpRequest.responseType = "json";

// ao receber a resposta com sucesso.:
// digamos que você passou o seguinte json.:
// { novoValor: 'Hello World' }.
var destino = document.getElementById("destino");
var campo = destino.querySelector("#id_campo");
campo.value = xmlHttp.response.novoValor;

As for returning a JSON in PHP, you can convert your object as follows:

echo json_encode($meu_objeto);

If you are going to use jQuery, you do it as follows:

$.ajax({
    type: 'POST',
    data: {
        aprova: true,
    },
    url: 'mudastatus.php',
    success: function(data){
       alert('ok');
    }

});

But there are a few other things you need to fix in your code.