Adding default value in comboConnector result

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 ?

My connector look like

$cnx= new PDOConfig();
$data = new ComboConnector($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

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

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