Laravel: Using try...catch with DB::transaction()

We all use DB::transaction() for multiple insert queries. In doing so, should a try...catch be placed inside it or wrapping it? Is it even necessary to include a try...catch when a transaction will automatically fail if something goes wrong?

Sample try...catch wrapping a transaction:

// try...catch
try {
    // Transaction
    $exception = DB::transaction(function() {

        // Do your SQL here

    });

    if(is_null($exception)) {
        return true;
    } else {
        throw new Exception;
    }

}
catch(Exception $e) {
    return false;
}

The opposite, a DB::transaction() wrapping a try...catch:

// Transaction
$exception = DB::transaction(function() {
    // try...catch
    try {

        // Do your SQL here

    }
    catch(Exception $e) {
        return $e;
    }

});

return is_null($exception) ? true : false;

Or simply a transaction w/o a try...catch

// Transaction only
$exception = DB::transaction(function() {

    // Do your SQL here

});

return is_null($exception) ? true : false;

Answers


In the case you need to manually 'exit' a transaction through code (be it through an exception or simply checking an error state) you shouldn't use DB::transaction() but instead wrap your code in DB::beginTransaction and DB::commit/DB::rollback():

DB::beginTransaction();

try {
    DB::insert(...);
    DB::insert(...);
    DB::insert(...);

    DB::commit();
    // all good
} catch (\Exception $e) {
    DB::rollback();
    // something went wrong
}

See the transaction docs.


If you use PHP7, use Throwable in catch for catching user exceptions and fatal errors.

For example:

DB::beginTransaction();

try {
    DB::insert(...);    
    DB::commit();
} catch (\Throwable $e) {
    DB::rollback();
    throw $e;
}

If your code must be compartable with PHP5, use Exception and Throwable:

DB::beginTransaction();

try {
    DB::insert(...);    
    DB::commit();
} catch (\Exception $e) {
    DB::rollback();
    throw $e;
} catch (\Throwable $e) {
    DB::rollback();
    throw $e;
}

You could wrapping the transaction over try..catch or even reverse them, here my example code I used to in laravel 5,, if you look deep inside DB:transaction() in Illuminate\Database\Connection that the same like you write manual transaction,

Laravel Transaction

public function transaction(Closure $callback)
    {
        $this->beginTransaction();

        try {
            $result = $callback($this);

            $this->commit();
        }

        catch (Exception $e) {
            $this->rollBack();

            throw $e;
        } catch (Throwable $e) {
            $this->rollBack();

            throw $e;
        }

        return $result;
    }

so you could write your code like this, and handle your exception like throw message back into your form via flash or redirect to another page. REMEMBER return inside closure is returned in transaction() so if you return redirect()->back() it won't redirect immediately, because the it returned at variable which handle the transaction.

Wrap Transaction

$result = DB::transaction(function () use ($request, $message) {
   try{

      // execute query 1
      // execute query 2
      // ..

      return redirect(route('account.article'));

   } catch (\Exception $e) {
       return redirect()->back()
          ->withErrors(['error' => $e->getMessage());
    }
 });

// redirect the page
return $result;

then the alternative is throw boolean variable and handle redirect outside transaction function or if your need to retrieve why transaction failed you can get it from $e->getMessage() inside catch(Exception $e){...}


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