Adding default value in comboConnector result

Hello,
I want to return a extra row with default value in the connector result and my connector is used by a combo.
Is there a solution on server side ?
thx

(PHP, PDO,DHTMLX3.0)
My connector look like

<?php
require_once('php/codebase/combo_connector.php');
require_once("php/codebase/db_pdo.php");
require_once("PDOConfig.php");
$cnx= new PDOConfig();
$res=$cnx->createcnxPDO();
$data = new ComboConnector($res,"PDO");
$data->render_sql("SELECT id_famille,lib_famille FROM famille","id_famille","lib_famille");
?>

And the XML expected result with extra option value “All”.This value is not in my database

<complete>
<option value="0">All</option>
<option value="1">FAMILY1</option>
<option value="2">FAMILY_2</option>
</complete>

It possible, but rather ugly

$data->render_complex_sql(" SELECT "0" as id_famille, "All" as lib_famille UNION SELECT id_famille,lib_famille FROM famille ","id_famille","lib_famille");

In such case , using custom php code may be a better solution.

Thanks i have also found this solution and if the custom php code is a better solution i can’t use filter with connector.
In first time i search in “event connector” like beforeRender and a function like

$action->add_item("name",$new_value) but no solution.

For this time i keep the sql solution.
Thanks Stanislav