$sql = "SELECT id, nom, cognom FROM usuaris";
 
$sql = "SELECT id, nom, cognom FROM usuaris";
−
$result = $conn->query($sql);
+
$result = $conn->prepare($sql);
 +
$result->execute();
 +
$result->bind_param($tid, $tnom, $tcognom);
   Exception encountered, of type "Error"