Pass variable trough functions

[eluser]InsiteFX[/eluser]

Code:

class some extends CI_Class {

    public $variabletopass = '';

    function index()
    {
        $variable = 'hello world'; //some X variable
        $this->variabletopass = $variable; //the variable that i need to pass through.
    }

    function misc()
    {
        $some = $this->$variabletopass; //this is what im trying but i dont get nothing
        var_dump($some);
    }
}