PDO Multiple queries: commit and rollback transaction

Question

I need to fire 2 queries. currently I'm doing it like this:

// Begin Transaction
$this->db->beginTransaction();

// Fire Queries
if($query_one->execute()){
    if($query_two->execute()){

        // Commit only when both queries executed successfully
        $this->db->commit();

   }else{
        $this->db->rollback();
   }
}else{
    $this->db->rollback();
}

Is this the correct approach? I'm not using any try..catch in my code will it make my code inappropriate or vulnerable for any situation?

Answer 1

Yes, your approach is correct. Using Try...catch may lead into cleaner and more readable code in some cases but your overall approach is fine.

If your code fragment is from a function that handles DB queries and not much else, I'd probably switch the approach around:

// Begin Transaction
$this->db->beginTransaction();

// Fire Queries
if(!$query_one->execute()){
    $this->db->rollback();
    // other clean-up goes here
    return;
}

if(!$query_two->execute()){
    $this->db->rollback();
    // other clean-up goes here
    return; 
}

$this->db->commit();

Of course, if you require lots of clean-up to be done before you can return, then your original approach is better. Especially in these cases I'd look into using PDO::ERRMODE_EXCEPTION. This has some additional benefits, like exceptions automatically rolling back the transaction unless they are caught.

Answer 2

You need to wrap your transaction inside a try-catch. Mostly, if an exception is thrown, there is something wrong that your process can not continue. You don't know where the exception will come from, right? So, instead of letting the exception thrown wildly and force the application to stop, it is better to catch it, rollback the database transaction, and rethrow it.

// Begin Transaction
$this->db->beginTransaction();

try {

    $queryOne->execute();
    $queryTwo->execute();

    $this->db->commit();

} catch (\Exception $e) {
    $this->db->rollback();
    throw $e;
}