Just FYI, I don’t use exceptions in CodeIgniter tho I’m using them a lot in Kohana, just because the framework throws them and everything is designed to work with exceptions unlike CodeIgniter. Using exceptions is a good practice providing all your classes/framework are designed to work with them.

I don’t (really, DON’T) want to enter in framework comparison discussions, but I need to compare two pieces of code to clarify your question, one piece from CI2 and another from Kohana 3 (it born as a branch of CI with better object oriented implementation).

You’ll see this CI2 code…

try
{
    $result = $this->db->insert('entries', $this->input->post());

    // This is not useful.
    if ( ! $result)
    {
        throw new Exception();
    }
}
catch (Exception $e)
{
    // Do something
}

It’s not very useful. Compare with this Kohana 3 code:

try
{
    $entry = ORM::factory('blog');
    $entry->values(Request::current()->post());
    $entry->save();
}
catch (ORM_Validation_Exception $e)
{
    Session::instance()->set('form_errors', $e->errors(TRUE));
}

You’ll see this is useful, you don’t throw the exception, it’s thrown by the class that handles the record saving and $e->errors has all the validation errors. When everything is designed to work with exceptions, you can be sure it’s a good practice and a very convenient one. But it’s not the case of CI2, so maybe I should say go ahead without using exceptions.

A possible approach to exceptions in CI…

try
{
    $this->load->model('blog');
    $this->blog->save_entry($this->input->post());   // Handle validation inside the model with the Form_validation library
}
catch (Validation_Exception $e)   // You throwed your custom exception with the failed validation information
{
    // Do something with your custom exception like the kohana example
    $this->session->set('form_errors', $e->errors());
}

I hope everything is understandable and maybe there’s someone with another interesting opinion and a more efficient implementation. Bye.