Firstly give names to buttons
<input type="submit" name="insert" value="Insert" />
<input type="submit" name="update" value="Update" />
<input type="submit" name="delete" value="Delete" />
and try the following function
public function create_users(){
$this->load->model('user_model');
if($this->input->post('insert') != ''){
/*Perform insert operation here*/
$username = $this->input->post('username');
$password = $this->input->post('password');
$data = array(
'username' => $username,
'password' => $password,
);
$this->users_model->insert_users($data);
}
else if($this->input->post('update') != ''){
/*perform update operation here*/
}
else if($this->input->post('delete') != ''){
/*perform delete operation here*/
}
$this->load->view('users_view');
redirect('users', 'refresh');
}