Ajax Framework (CJAX) for Codeigniter 2.x+

[eluser]fran-quero[/eluser]
Hello. Give me a hand with this, please.

I'm trying to use $this->input->post in my ajax controller (application/response/controller), but I always get undefined.

Code:

$ajax->alert($form_fields['name']); //print value successfully
$ajax->alert($this->input->post('a[name]')); //print undefined
$ajax->alert($this->input->post($form_fields['name'])); //print undefined

Can't I use input->post in the ajax controller?