Cannot login in my site

[eluser]jim04[/eluser]
Hello,

I 'm new in CI and and i study according to some video tutorials. Even if the topic is similar to others the answers couldn't help me, so i decided to post it again to solve the problem

I have this Controller

Code:

<?php

class Login extends CI_Controller{

function index(){
  $data['main_content'] = 'login_form';
  $this->load->view('includes/template', $data);
}

function validate_credentials(){
  $this->load->model('membership_model');
  $query = $this->membership_model->validate();

  if($this->membership_model->validate()){
   $data = array(
   'username' => $this->input->post('username'),
   'is_logged_in' => true
   );
   $this->session->set_userdata($data);
            
   redirect('site/members_area');

  }
  
  else{
   $this->index();

  }
  
}

and this model

Code:

<?php

class Membership_model extends CI_Model{

function validate(){  
  $this->db->where('username', $this->input->post('username'));
  $this->db->where('password', md5($this->input->post('password')));
  $query = $this->db->get('membership');

  if ($query->num_rows == 1){
   return true;
  }  
}

}

when i try to login it takes me to tis URL http://localhost/ci_day6/index.php/login...redentials either the username and password are true or not.

Please help me!