Laravel 5.1 redirect within a transaction block

I have a set of delete statements in my Laravel 5.1 application that I have put inside a transaction.

I had my code like the following and was trying to return to the same page. But I was getting a blank page. My routes.php is fine.

DB::transaction(function () use ($foo, $bar, $request)  
{   
    // Delete from table abc
    $deletedFoo = DB::delete('delete from abc where id = ' .  $foo);

    // Delete from table xyz
    $deletedBar = DB::delete('delete from xyz where id = ' .  $bar);

    // Shows blank page
    $request->session()->flash('changes_saved', 'Success! All your changes were saved.');
    return back();

});

However, if I put the return starement outside the DB::transaction block it works fine.

DB::transaction(function () use ($foo, $bar)    
{   
    // Delete from table abc
    $deletedFoo = DB::delete('delete from abc where id = ' .  $foo);

    // Delete from table xyz
    $deletedBar = DB::delete('delete from xyz where id = ' .  $bar);
});

// Goes back to the page with the message
$request->session()->flash('changes_saved', 'Success! All your changes were saved.');
return back();

I tried various things before I realized I need to put the redirect outside the transaction. But why? I am new to Laravel and bit confused here.

via Chebli Mohamed