how I want the user id become static - cakephp

Question

I'm kind new to the cakephp and I want to know how to static the id where the id is on drop down or list. I have do hidden but its not enter the database. This is my coding:
This is in the controller
function add() {
if (!empty($this->data)) {
$this->Post->create();
if ($this->Post->save($this->data)) {
$this->Session->setFlash(__('The post has been saved', true));
$this->redirect(array('action' => 'index'));
} else {
$this->Session->setFlash(__('The post could not be saved. Please, try again.', true));
}
}
$users = $this->Post->User->find('list');
$this->set(compact('users'));
$this->set('userid',$this->Auth->user('id'));
}
this coding is in the ctp
<?php
echo $this->Form->input('user_id');
?>

Answer 1

The best way is to not send the user id to the browser and back at all, since that opens the possibility of form tinkering and security breaches/invalid results. Just inject the user id into the data before saving:
function add() {
if (!empty($this->data)) {
$this->Post->create();
// setting user id
$this->data['Post']['user_id'] = $this->Auth->user('id');
if ($this->Post->save($this->data)) {
$this->Session->setFlash(__('The post has been saved', true));
$this->redirect(array('action' => 'index'));
} else {
$this->Session->setFlash(__('The post could not be saved. Please, try again.', true));
}
}
$users = $this->Post->User->find('list');
$this->set(compact('users'));
}