class checkReturn {
    public $var = "some value";

    function what_return_return() {
        return $this->var = "some value";
    }

    function to_upper_case() {
        return strtoupper($this->var);
    }

    function to_lower_case() {
        return strtolower($this->var);
    }

}

$check = new checkReturn();
var_dump($check->to_upper_case()->to_lower_case());