Unset sessions after form success not working - codeigniter

Question

When I deselect my check box in my modify & access permissions it does not unset it from sessions if form is submitted success full.
What I am trying to achieve is on my edit function if any check box is not checked then it will unset from sessions when form is submitted success full. Because the reason need it unset from sessions is because when user logs in the permissions modify and access are set into sessions.
How can I make this work what I am after I have tried it in my edit but not unset when check box is empty
If i use this $this->session->unset_userdata('modify'); it unset all the modify array in sessions I just need it to unset the one that matches the unchecked check box.
public function edit() {
$this->load->model('admin/user/model_user_group');
if ($this->input->server('REQUEST_METHOD') == 'POST') {
$this->model_user_group->editUserGroup($this->uri->segment(4), $this->input->post());
if ($this->session->userdata('user_id') == TRUE) {
if (isset($_POST['permission[access]'])) {
$this->session->unset_userdata('permission[access]');
}
if (isset($_POST['permission[modify]'])) {
$this->session->unset_userdata('permission[modify]');
}
}
redirect('admin/users_group');
}
$this->getForm();
}
public function getForm() {
$data['title'] = "Users Group";
$this->load->model('admin/user/model_user_group');
$user_group_info = $this->model_user_group->getUserGroup($this->uri->segment(4));
if ($this->uri->segment(4) == FALSE) {
$data['name'] = $this->input->post('name');
} else {
$data['name'] = $user_group_info['name'];
}
if ($this->uri->segment(4) == FALSE) {
$data['user_group_id'] = $this->input->post('user_group_id');
} else {
$data['user_group_id'] = $user_group_info['user_group_id'];
}
$ignore = array(
'admin',
'dashboard',
'filemanager',
'login',
'menu',
'register',
'online',
'customer_total',
'user_total',
'chart',
'activity',
'logout',
'footer',
'header',
'permission'
);
$data['permissions'] = array();
$files = glob(FCPATH . 'application/modules/admin/controllers/*/*.php');
foreach ($files as $file) {
$permission = basename(strtolower($file), '.php');
if (!in_array($permission, $ignore)) {
$data['permissions'][] = $permission;
}
}
$permission_access = $this->input->post('permission');
if (isset($permission_access)) {
if (isset($permission_access['access'])) {
$data['access'] = $permission_access['access'];
} elseif (!empty($user_group_info['permission']['access'])) {
$data['access'] = $user_group_info['permission']['access'];
} else {
$data['access'] = array();
}
}
$permission_modify = $this->input->post('permission');
if (isset($permission_modify)) {
if (isset($permission_modify['modify'])) {
$data['modify'] = $permission_modify['modify'];
} elseif (!empty($user_group_info['permission']['modify'])) {
$data['modify'] = $user_group_info['permission']['modify'];
} else {
$data['modify'] = array();
}
}
$this->load->view('template/user/users_group_form.tpl', $data);
}

Answer 1

I have found away to get it working I have got sessions from database then re set the sessions in form, without using unset_sessions();
public function edit() {
$this->load->model('admin/user/model_user_group');
if ($this->input->server('REQUEST_METHOD') == 'POST') {
$this->model_user_group->editUserGroup($this->uri->segment(4), $this->input->post());
$user_group_query = $this->db->query("SELECT permission FROM " . $this->CI->db->dbprefix . "user_group
WHERE user_group_id = '" . (int)$this->session->userdata('user_group_id') . "'");
$permissions = unserialize($user_group_query->row('permission'));
$this->session->set_userdata($permissions);
redirect('admin/users_group');
}
$this->getForm();
}