How can i send the compositefield value to JSON to obtain values?

[crynof]

Hi!, y trying to send a composite values to JSON to catch some DB values and the fill a textfields in the form.

This is the Composite field

{                                    columnWidth: 0.2,
                                    layout: 'form',
                                    items: [{
                                            xtype: 'compositefield',
                                            fieldLabel: 'Rut',
                                            msgTarget: 'under',
                                            items: [{
                                                    xtype: 'textfield',
                                                    name: 'rut',
                                                    id: 'id_rut',
                                                    width: 150
                                                },
                                                {xtype: 'displayfield', value: '-'
                                                },
                                                {
                                                    xtype: 'textfield',
                                                    name: 'dv',
                                                    id: 'id_dv',
                                                    width: 50
                                                }]
                                        }]
                                }

Here the store

var store_datosPersonales = new Ext.data.Store  // ({
    proxy: new Ext.data.HttpProxy({
        url:  'json/DatosPersonales.php?accion=cargarPersonales',
        method: 'POST'
    }),
    reader: new Ext.data.JsonReader
    ({
        fields: ['rut','dv'],
        root: 'rows'       
    }),
            autoLoad: true
});

and the json

<?phpinclude_once("../../libfinanzas/inc_readme.php");
$link = conectarse_Finanzas();


$accion = $_REQUEST['accion'];
$rut = $_REQUEST['mper_rut'];
$dv = $_REQUEST['mper_dv'];




if($accion=='cargarPersonales') // listo
{
$SQL_datosPersonales = "SELECT mp.mper_apellido_paterno, mp.mper_apellido_materno, mp.mper_nombres, mp.esci_codigo FROM 
                      comun.dbo.maestro_personas AS mp where mp.mper_rut = $rut AND mp.mper_dv = $dv" ;  


// **** Funcion Crear JSON ****


$respuesta = CreaJSon($SQL_datosPersonales, $link, 'rows',1);
   echo $respuesta;


?>

the problem is that i dont know how are connected the variables between these files.

How can i connect this files?

PD: CreaJson is a Library function that send the request values to form.

Thanks!!