jQuery Grid Plugin - jqGrid

Hello, please, I need to show errors from my database mysql , for example 'Duplicate entry' or 'Already exists' in XML, because I have the way to show errors in JSON but I need to do it in XML.

Source code:

Javascript

var json;
var editMessage = function(response,postdata){
    json   = response.responseText; // response text is returned from server.
    var result = JSON.parse(json); // convert json object into javascript object
    return [result.status,result.message,null];
}
//--------------------------------------
jQuery.jgrid.edit = {
editCaption: "Editar",
bSubmit: "Guardar",
bCancel: "Cerrar",
closeAfterEdit:true,
reloadAfterSubmit:true,
processData: "Processing...",
msg:{required:"El campo es obligatorio"},
afterSubmit:editMessage
};

PHP

$message="Duplicate Entry";

$output['status']  = false;
$output['message'] = $message;
echo json_encode($output);