How to get outside login data (session) in WordPress?

i want to use codeignider login form session in wp login form

public function check_login()
{     

    if($this->session->userdata('logged_in'))
    {
        redirect('/');
    }
    //Set Page Title
    $data['title'] = "Check Login"; 

     $username = $this->input->post('username');
     $email = $this->input->post('username');
     $password = $this->input->post('password');        
     $password = hash('sha1',$password);
    echo (int)$is_admin = $this->loginmodel->user_login($username, $email, $password);
       $_SESSION['sumit']['puri']=$this->session->userdata('id');
    // print_r($is_admin);
    //
}