Hello, i have this message error and i don't know where does the problem comes from:

    <?php include "DBconnection.class.php";

$sql = DBConnection::getInstance(); 

$requete = "SELECT g.siteweb,
                    g.offreDedie, 
                    g.coupon, 
                    g.only_dedi,
                    g.transparence, 
                    g.abonnement ,
                    s.GSP_nom as nom ,
                    COUNT(s.GSP_nom) as nb_votes,
                    TRUNCATE(AVG(vote), 2) as qualite,       
                    TRUNCATE(AVG(prix), 2)  as rapport, 
                    TRUNCATE(AVG(serviceClient), 2) as serviceCli,  
                    TRUNCATE(AVG(interface), 2)  as interface, 
                    TRUNCATE(AVG(services), 2)  as services
                    FROM votes_serveur AS v
                    INNER JOIN serveur AS s ON v.idServ = s.idServ
                    INNER JOIN gsp AS g ON s.GSP_nom = g.nom
                    WHERE s.valide = 1
                    GROUP BY s.GSP_nom";



 $sql->query($requete);




 $xml = '<?xml version="1.0" encoding="UTF-8" ?><GamerCertified>';


            while($row = $sql->fetchArray()){

                $moyenne_services =  ($row['services'] + $row['serviceCli']  + $row['interface'] )  / 3 ;
                $moyenne_services = round( $moyenne_services, 2);

                $moyenne_ge =  ($row['services'] + $row['serviceCli']  + $row['interface'] + $row['qualite'] + $row['rapport'] )  / 5 ;
                $moyenne_ge = round( $moyenne_ge, 2);

                 $xml .= '<GSP>';

                 $xml .= '<nom>'.$row["nom"].'</nom>';

                 $xml .= '<nombre-votes>'.$row["nb_votes"].'</nombre-votes>';

                 $xml .= '<services>'.$moyenne_services.'</services>';

                 $xml .= '<qualite>'.$row["qualite"].'</qualite>';

                 $xml .= '<prix>'.$row["rapport"].'</prix>';

                 $xml .= '<label-transparence>'.$row["transparence"].'</label-transparence>';

                  $xml .= '<moyenne-generale>'.$moyenne_ge.'</moyenne-generale>'; 

                 $xml .= '<serveurs-dedies>'.$row["offreDedie"].'</serveurs-dedies>';

                 $xml .= '</GSP>';
            }

 $xml .= '</GamerCertified>';

 echo $xml;

Thanks