How to make transactions in Doctrine 2 using Symfony 2

transaction.php

<?php

// Snippet for Symfony 2 application that uses Doctrine 2 to handle transactions
// It uses the names of the objects/doctrine repositories from the Beta 4 Manual of Symfony 2.

// Get the entity manager
$em = $this->getDoctrine()->getEntityManager();

// suspend auto-commit
$em->getConnection()->beginTransaction();

// Try and make the transaction
try {
    // Get the account
    $account = $this->getDoctrine()->getRepository('AcmeStoreBundle:Account')->find($id);

    // Lower balance
    $account->setBalance($account->getBalance() - 100);

    // Save account
    $em->persist($account);
    $em->flush();

    // Try and commit the transaction
    $em->getConnection()->commit();
} catch (Exception $e) {
    // Rollback the failed transaction attempt
    $em->getConnection()->rollback();
    throw $e;
}

@Steveb-p

From your link:

Database transactions are fine for concurrency control during a single request. However, a database transaction should not span across requests, the so-called “user think time”. Therefore a long-running “business transaction” that spans multiple requests needs to involve several database transactions. Thus, database transactions alone can no longer control concurrency during such a long-running business transaction. Concurrency control becomes the partial responsibility of the application itself.

So, IMHO, it doesn't have anything to do with "being absolutely sure that whatever your process is trying to do is done on most recent database data", it only depends on if you need transactions on multiple requests or not, right?