use config file for constants in codeigniter
===

I am using cibonfire, 
I have to use some constants in my programs which can be changed later.
So what I am doing is I am writing my config file inside `application/config/roles.php`
and using that config file in my modules to get that constants, but I am not getting the required result.

here is my config file `roles.php` :-

    <?php 
    $config['roles.permission'] =  array (
					"Super Admin" => array('role_name' => 'Administrator','role_id' => 1),
					"Banned Users" => array('role_name'=>'Banned','role_id'=>3),
					"User" => array('role_name' => 'User' , 'role_id' => 4 ),
					"Bimalogy Admin" => array('role_name' => 'Bimalogy Admin' ,'role_id' => 7),
					"Bimaadda Admin " => array('role_name' => 'Bimaadda Admin', 'role_id' => 8),
					"Licagent Admin" => array('role_name' => 'Licagent Admin' , 'role_id' => 9),
					"Bimalogy Moderators" => array('role_name'=>'Bimalogy Moderators','role_id'=>10),
					"Bimaadda Moderators" => array('role_name' => 'Bimaadda Moderators' ,'role_id' => 11),
					"Licagent Moderators" => array('role_name'=> 'Licagent Moderators','role_id'=>12),
				);
    ?>

Now when I am doing this my view file:-
`$role = $this->config->item('roles.permission)`

`echo $role['Bimalogy Admin']['role_name];` I should have get Bimalogy Admin as output but 
output screen shows nothing.

When I am doing this :-

`var_dump($this->config->item('roles.permission'))`
output is `boolean false`

What mistake I am committing.?
