Error with dependent dependent php, sqlsrv, jquery

I wanted to exercise with this library sqlsrv since with mysqli I worked without problem the exercise of the dependent select for regions, provinces and communes. My problem is the following I do not know how to debug with jquery in order to capture the error correctly but nevertheless I suppose that the data is sent and the one created in the other page appears where it is being rendered (getProvincia.php)

JQUERY

 $(document).ready(function(){
 $("#region").change(function () {
                $("#region option:selected").each(function () {
id_region = $(this).val();
$.post("lib/getProvincia.php", { id_region: id_region }, function(data){
$("#provincia").html(data);
});            
});
});

});                               

getProvincia.php     

$query= "SELECT     ProvCod, ProvDes, Id_Region FROM  provincia WHERE     
Id_Region = '$id_region' ORDER BY ProvDes";

$stmt = sqlsrv_query($con,$query);

$html= "<option value='0'>Seleccionar Provincia</option>";// esta opcion aparece  como option al seleccionar cualquier region

while($row = sqlsrv_fetch_array($stmt,SQLSRV_FETCH_ASSOC))
{
 $html.= "<option value='".$row['ProvCod']."'>".$row['ProvDes']."</option>";
 }


 echo $html;

 ?>

HTML

      <form  method="post" >
  <div class="form-group">
  <label class="col-sm-3 control-label" for="region">Región :</label>
  <div class="col-sm-3">
 <select class="form-control" id="region"  name="region">
 <option value="0">Seleccione</option>
 <?php get_region();?> //este select si le llena correctamente
  </select>
     </div>

<label class="col-sm-3  control-label" for="provincia">Provincia :</label>
<div class="col-sm-3">
<select class="form-control"  name="provincia" id="provincia">
</select>
    </div>
</div>

</form>


function get_region(){
$con=conectar();
$query_reg = "SELECT     id_Region, Descripcion FROM region";
if($stmt_reg = sqlsrv_query($con,$query_reg)){
  while($row = sqlsrv_fetch_array($stmt_reg)){

?> <option value="<?php echo $row['id_region']; ?>" > <?php echo 
$row['Descripcion']; ?> </option> <?php 

  }
}

}