jQuery Grid Plugin - jqGrid

I've a grid with a subgrid. I've enabled the 'add' and 'edit' options in the subgrid, show the form correctly but when clicked the save button the data are not saved in the database.

Why?

the grid code: gridavisos.php

<?php
require_once 'jq-config.php';
// include the jqGrid Class
require_once ABSPATH."jqGrid.php";
// include the driver class
require_once ABSPATH."jqGridPdo.php";
// Connection to the server
$conn = new PDO(DB_DSN,DB_USER,DB_PASSWORD);
// Tell the db that we use utf-8
$conn->query("SET NAMES utf8");
// Create the jqGrid instance
$grid = new jqGridRender($conn);
// this table is 1252 encoded, so we need to tell the grid
// Set the table data source
$grid->setTable('clientes');
// set the ouput format to xml since json have problems
$grid->dataType = 'xml';
// Let the grid create the model
$grid->setColModel();
// Set the url from where we obtain the data
$grid->setUrl('gridavisos.php');
// Set some grid options
$grid->setGridOptions(array("height"=>400,"hoverrows"=>true,"autowidth"=>true,"rowNum"=>20,"rowList"=>array(20,50,100),"sortname"=>"nombre"));
$grid->setColProperty("cif", array("width"=>90));
$grid->setColProperty("cp", array("width"=>45));
$grid->setColProperty("provincia", array("width"=>80));
$grid->setColProperty("telefono", array("width"=>60));
// We can hide some columns
$grid->setColProperty("id_cliente", array("hidden"=>true));
// set labels in the header
$grid->setColProperty("nombre", array("label"=>"Nombre"));
$grid->setColProperty("cif", array("label"=>"NIF"));
$grid->setColProperty("direccion", array("label"=>"Dirección"));
$grid->setColProperty("cp", array("label"=>"CP"));
$grid->setColProperty("poblacion", array("label"=>"Población"));
$grid->setColProperty("provincia", array("label"=>"Provincia"));
$grid->setColProperty("email", array("label"=>"Email"));
$grid->setColProperty("telefono", array("label"=>"Teléfono"));
// Enable toolbar searching
$grid->toolbarfilter = true;
$grid->setFilterOptions(array("stringResult"=>true));
$grid->setSubGridGrid("subgridavisos.php");
// Enjoy
$grid->renderGrid('#grid','#pager',true, null, null, true,true);
$conn = null;
?>

the subgrid code: gridsubavisos.php

<?php
require_once 'jq-config.php';
// include the jqGrid Class
require_once ABSPATH."jqGrid.php";
// include the driver class
require_once ABSPATH."jqGridPdo.php";
// Connection to the server
$conn = new PDO(DB_DSN,DB_USER,DB_PASSWORD);
// Tell the db that we use utf-8
$conn->query("SET NAMES utf8");
// Get the needed parameters passed from the main grid
// By default we add to postData subgrid and rowid parameters in the main grid
$subtable = jqGridUtils::Strip($_REQUEST["subgrid"]);
$rowid = jqGridUtils::Strip($_REQUEST["rowid"]);
if(!$subtable && !$rowid) die("Missed parameters");
// Create the jqGrid instance
$grid = new jqGridRender($conn);
// Write the SQL Query
$grid->SelectCommand = "SELECT * FROM avisos WHERE id_cliente = ?";
// set the ouput format to json
$grid->dataType = 'json';
// Let the grid create the model
$grid->setColModel(null,array(&$rowid));
// Set the url from where we obtain the data
$grid->setUrl('subgridavisos.php');
// Set some grid options
$grid->setGridOptions(array(
    "hoverrows"=>true,"autowidth"=>true,
    "rowNum"=>10,
    "sortname"=>"id_aviso",
    "height"=>70,
    "postData"=>array("subgrid"=>$subtable,"rowid"=>$rowid)));
// Change some property of the field(s)
$grid->setColProperty("fecha", array(
    "formatter"=>"date",
    "formatoptions"=>array("srcformat"=>"Y-m-d","newformat"=>"d/m/Y"),
    "search"=>false
    )
);
$grid->setColProperty("fecha", array("width"=>15));
// We can hide some columns
//$grid->setColProperty("id_aviso", array("hidden"=>true));
//$grid->setColProperty("id_cliente", array("hidden"=>true));
// set labels in the header
$grid->setColProperty("fecha", array("label"=>"Fecha"));
$grid->setColProperty("descripcion", array("label"=>"Descripción"));
$grid->navigator = true;
$grid->setNavOptions('navigator', array("excel"=>false,"add"=>true,"edit"=>true,"del"=>true,"view"=>true));
//config dialogs
$grid->setNavOptions('add',array("closeOnEscape"=>true,"closeAfterAdd"=>true,"reloadAfterSubmit"=>true));
$grid->setNavOptions('edit',array("checkOnSubmit"=>true,"closeOnEscape"=>true,"closeAfterEdit"=>true,"reloadAfterSubmit"=>true));
$grid->setNavOptions('view',array("closeOnEscape"=>true));
// Enjoy
$subtable = $subtable."_t";
$pager = $subtable."_p";
$grid->renderGrid($subtable,$pager, true, null, array(&$rowid), true,true);
$conn = null;
?>

database:

table: clientes

   id_cliente, nombre, cif, direccion, cp, poblacion, provincia, email, telefono

table: avisos

   id_aviso, id_cliente, fecha, descripcion