Parse error: syntax error, unexpected '::'

Hello, 
I defined constants in Otobil_model.php

PHP Code:

class Otobil_model extends MY_Model
{

    const INDIVIDUAL_TYPE = 'INDIVIDUAL';
    const CORPORATE_TYPE = 'CORPORATE';
} 


Then in Controller I am trying to access these constants:

PHP Code:

class Otobil extends Public_Controller
{
    function __construct()
    {
        parent::__construct();
        $this->load->model('otobil_model');
    }

    public function apply()
    {
        $type = $this->otobil_model::CORPORATE_TYPE;     
    }
} 


I am getting " Parse error: syntax error, unexpected '::' (T_PAAMAYIM_NEKUDOTAYIM) in \application\controllers\Otobil.php on line 36"

Anybody has idea why I am getting this error? 
I already did this in my other projects, but now I am getting this error...