data insertion using ajax and php

I have a problem. I have to make an attendance report, based on the marking done by the employee at the time of entering, I must perform the assistance (if it is or is not). to insert the assistance, I need to do it through ajax but I could not.

this is my query code

$i=0;
             $n=0;
             while($fila=$consulta->fetch(PDO::FETCH_ASSOC))
             {
                 $this->empleados[]=$filas;
                 $Filas = consult_cedula($fila['Persona']);

                 echo "<tr>";
                 echo '<td>' . $Filas['codsucursal'] . '</td>';
                 echo '<td>' . $fila['Persona'] . '</td>';
                 echo '<td>' . $fila['Fecha'] . '</td>';
                 echo '<td>' . $fila['Hora'] . '</td>';
                 echo '<td>' . $Filas['nombre'] . '</td>';
                 echo '<td>' . $Filas['cargo'] . '</td>';

                echo '<td>' . '<input type="button" name="nom'.$n.'" id="btn'.$n.'" class="btn btn-danger" value="..." data-fech="' .
                  $fila['Fecha'] . '" data-hora="' . $fila['Hora'] . '" data-ced="' . $fila['Persona'] .
                  '" data-nom="' . $Filas['nombre'] . '" data-cargo="' . $Filas['cargo'] .'" onclick="myFunction('.$n.')">';

                 echo "</tr>";


                 $i=$i+1;
                 $n=$n+1;


             }

this is my ajax code

function myFunction(valor){

var z = valor;
var connect, button, response, result;
var fech = $('#btn' + valor).data("fech");
var hora = $('#btn' + valor).data("hora");
var ced = $('#btn'+valor).data("ced");
var nom =$('#btn' + valor).data("nom");
var cargo = $('#btn' + valor).data("cargo")

var data = fech+hora+ced+nom+cargo;

console.log(data);

  connect = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject('Microsoft.XMLHTTP');
  connect.onreadystatechange = function() {
         // ESTADO DE LA CONEXION
    if(connect.readyState==4 && connect.status == 200) {
         if(connect.responseText == 1) {
             result  = '<div class="alert alert-dismissible alert-success">';
             result += '<button type="button" class="close" data-dismiss="alert">&times;</button>;'
             result += '<h4 class="alert-heading">Registrando</h4>';
             result += '<p> Estamos Procesando tu Registro </p>';
             result += '</div>';
             __('_AJAX_REG_').innerHTML = result;
             location.reload();
         } else {
        __('_AJAX_REG_').innerHTML = connect.responseText;
            }
    } else if (connect.readyState!=4) {
     result  = '<div class="alert alert-dismissible alert-warning">';
     result += '<button type="button" class="close" data-dismiss="alert">&times;</button>;'
     result += '<h4 class="alert-heading">Procesando...</h4>';
     result += '<p> Procesando Registro </p>';
     result += '</div>';
     __('_AJAX_REG_').innerHTML = result;
      }

    }
    connect.open('POST','formatosTH/marcaje/ajax.php',true);
    connect.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
    connect.send(data);


}

which redirects me to this file (which is ajax.php)

 <?php 

    if($_POST) {
        echo 1;
    } else {
         echo 'No hay nada';
    }

 ?>

which I verify if something arrives by POST. but a NULL value arrives.

How could I solve it?