我有以下几点 update of the users table 和一个 selection 这给了我 updated result 就在更新之后，我想知道使用 transaction 在这里？如果是的话，那我用对了吗 codewisely together with prepared statements ?

try {

        // connect to the database
        require 'connect.php';
        // create an update query
        $conn->beginTransaction();
        $queryUpdate = $conn->prepare("UPDATE users SET userName=:userName, firstName=:firstName,
        lastName=:lastName, password=:password, image=:image  WHERE userId=:userId"); 
        $queryUpdate->bindParam( ':userId' , $sUserId );
        $queryUpdate->bindParam( ':userName' , $sNewUserName );
        $queryUpdate->bindParam( ':firstName' , $sNewFirstName );
        $queryUpdate->bindParam( ':lastName' , $sNewLastName );
        $queryUpdate->bindParam( ':password' , $sNewPassword );
        $queryUpdate->bindParam( ':image' , $sNewImagePath );
        $bResult = $queryUpdate->execute();
        // create another query to get some of the updated values
        $querySelect = $conn->prepare("SELECT users.userName, users.firstName, users.lastName, users.image
        FROM users WHERE userId=:userId");
        $querySelect->bindParam( ':userId' , $sUserId );
        // run query 
        $querySelect->execute();  
        $ajResult = $querySelect->fetch(PDO::FETCH_ASSOC);
        // take each property one by one
        $sUserName = $ajResult['userName'];
        $sFirstName = $ajResult['firstName'];
        $sLastName = $ajResult['lastName'];
        $sImagePath = $ajResult['image'];
        // i.e. no query has failed, and we can commit the transaction
        $conn->commit();
        $sjResponse = $bResult ? '{"status":"ok", "userName":"'.$sUserName.'", "firstName":"'.$sFirstName.'",
         "lastName":"'.$sLastName.'", "image":"'.$sImagePath.'"}' : '{"status":"error"}'; 
        echo $sjResponse;
} catch (Exception $e) {
        // An exception has been thrown
        // We must rollback the transaction
        echo "ERROR";
        $conn->rollback();

}