Fatal error :Call to undefined function sc_select in Class ?????

Hello,

I call a function in a class , but it’s gives an error message on sc_select command ???
Fatal error: Call to undefined function sc_select

Do I include something else ?

Here are the code :

In form :

$WOobj=new WOClass();
$p_codlibre=$WOobj->UTLecParam(“P_CODLIBRE”);

In Librairies :

class WOClass{
3|
4| function UTLecParam($valparam){
5| $requete = “SELECT cvaleur,ctaille FROM tparamet WHERE cnom = '”.$valparam."’";
6| sc_select(my_data, $requete, “conn_mysql”);
7| if (!$my_data->EOF){
8| $valretour=trim($my_data->fields[0]);
9| }
10| else {
11| $valretour="";
12| }
13| $my_data->Close();
14|
15| return $valretour;
16| }
17| …

}

Thanks in advance