CakePHP prepopulate form with data from a link - php

Question

Assume I'm in my items controller.
Ok say I am in my view action (the url would be something like /items/view/10012?date=2013-09-30) which lists a list of items that belongs to a client on a given date.
I want to link to add a new item. I would use the htmlhelper like so:
echo $this->Html('action'=>'add');
In my add action I have a form which has fields like client_id and item_date.
When I'm in my view action I know these values as I am viewing the items for a specific client on a specific date. I want to pass these variables to my add action so it will prefill those fields on the form.
If I add a query string in my link ('?' => array('client_id'=>$client_id)) it breaks the add action as it will give an error if the request is not POST. If I use a form->postLink I get another error as the add action's POST data must only be used for adding the record, not passing data to prefill the form.
I basically want to make my link on the view page pass those 2 variables to the add action in the controller so I can define some variables to prefill the form. Is there a way to do this?
Here is my add controller code. It may differ in content a bit from my question above as I have tried to simplify the question a bit but the concept should still apply.
public function add(){
if ($this->request->is('post')) {
$this->Holding->create();
if ($this->Holding->save($this->request->data)) {
$this->Session->setFlash(__('Holding has been saved.'), 'default', array('class' => 'alert alert-success'));
return $this->redirect(array('action' => 'index'));
}
$this->Session->setFlash(__('Unable to add your holding.'), 'default', array('class' => 'alert alert-danger'));
}
$this->set('accounts', $this->Holding->Account->find('list'));
$sedol_list = $this->Holding->Sedol->find('all', array(
'fields' => array(
'id', 'sedol_description'
),
'recursive' => 0,
'order' => 'description'
)
);
$this->set('sedols', Hash::combine($sedol_list, '{n}.Sedol.id', '{n}.Sedol.sedol_description') );
}

Answer 1

Why not use proper Cake URL parameters?
echo $this->Html->link('Add Item', array(
'action' => 'add',
$client_id,
$item_date
));
This will give you a much nicer URL like:
http://www.example.com/items/add/10012/2013-09-30
And then in your controller, you modify the function to receive those parameters:
public function add($client_id, $item_date) {
// Prefill the form on this page by manually setting the values
// in the request data array. This is what Cake uses to populate
// the form inputs on your page.
if (empty($this->request->data)) {
$this->request->data['Item']['client_id'] = $client_id;
$this->request->data['Item']['item_date'] = $item_date;
} else {
// In here process the form data normally from when the
// user has submitted it themselves...
}
}