CI - show database error or fail - php

Question

I've developed a simple login system which works ok but fails, and I need to know why
QUESTION: How to show what is causing the fail. This is not a validation error but an error either with the data being passed to MySQL or the query somehow failing
here's the db function:
function login($email,$password)
{
$this->db->where("email",$email);
$this->db->where("password",$password);
$query=$this->db->get("users");
if($query->num_rows()>0)
{
foreach($query->result() as $rows)
{
//add all data to session
$newdata = array(
'user_id' => $rows->id,
'user_name' => $rows->username,
'user_email' => $rows->email,
'logged_in' => TRUE,
);
}
$this->session->set_userdata($newdata);
return true;
}
return false;
}
And here's the logic:
public function login()
{
$this->load->library('form_validation');
// field name, error message, validation rules
$this->form_validation->set_rules('email', 'Your Email', 'trim|required|valid_email');
$this->form_validation->set_rules('password', 'Password', 'trim|required|min_length[4]|max_length[32]');
if($this->form_validation->run() == FALSE)
{
$this->signin();
}
else
{
$email=$this->input->post('email');
$password=md5($this->input->post('pass'));
$result=$this->user_model->login($email,$password);
if($result)
{
$this->dash();
}
else
{
$data['title']= 'Login Error';
$this->load->view('nav/header', $data);
$this->load->view('login', $data);
$this->load->view('nav/footer', $data);
}
}
}
I know the error is happening as I redirect back to login page if fail and change title text to show me (only in testing mode for right now) - but how can I find out what is going wrong with the query?

Answer 1

You can use log_message and check the logs if the y behave as expected:
http://ellislab.com/codeigniter/user-guide/general/errors.html
I usually just use echo '<pre>'; print_r($query->result());die; just after the $query is formed.
It's faster.

Answer 2

$this->db->where("email",$email);
$this->db->where("password",$password);
$query=$this->db->get("users");
echo $this->db->last_query();
die();
you can echo the query you just did by using $this->db->last_query() this will show the query that your made with the values, and check if the query is valid.
read more at http://ellislab.com/codeigniter/user-guide/database/helpers.html