Object Property Scope-Collection of common programming errors

I want to declare a private variable inside class which I want to access in all of my class without passing it to another function using parameter. I have following scenario

class One extends CI_Controller {
    private $name;
    public function index () {
        $name = $this->input->post('name');

    public function validate() {
        echo $name;

But my above $name variable gives me an error saying variable $name is undefined.

Is above possible in PHP if yes then how?

Originally posted 2013-11-09 21:06:31.