Eliminar cache, evitar botón atrás

Cache.php

    
    public function removeCache()
    {
        $this->output->set_header('Last-Modified:'.gmdate('D, d M Y H:i:s').'GMT');
        $this->output->set_header('Cache-Control: no-store, no-cache, must-revalidate');
        $this->output->set_header('Cache-Control: post-check=0, pre-check=0',false);
        $this->output->set_header('Pragma: no-cache');
    }