I have read some other related questions on stackoverflow but none solved my problem. This is my code:
$stmt = $conexion->prepare("SELECT Email, MaxActiv FROM `Keys` WHERE ProdKey = ?");
                $stmt->bind_param('sss', $varKey);
                $stmt->execute();
                //$stmt->bind_result($Email, $MaxActiv);
                $stmt->store_result();
                echo "rows: " . $stmt->num_rows . " - " . $Email;
                //Comprobamos si la key existe (esta comprada)
                if ($stmt->num_rows > 0 ){
but it always returns 0 even if the key actually exists on database
