How to make paging from the basics

Everything works, the only thing I can not fix is the url, in fact every page is shown as: mysite.com/per_page?=5
I could not do something like mysite.com/page/2

Il mio controller

PHP Code:

   public function index() {
        $offset = 0;
        if ($this->input->get('per_page') != null) {
            $offset = $this->input->get('per_page');
        }
        
        $count = 5; //number of posts in page 
        $filter = array();
        $data['post_count'] = $this->post_model->get_active_posts($filter);
        $data['title'] = 'Title';
        $data['desc'] = 'Enter the description of this page index';
        $data['post'] = $this->post_model->get_index($filter, $count, $offset); 
        $config['base_url'] = base_url();
        $config['total_rows'] = $data['post_count'];
        $config['per_page'] = $count;
        $config['next_link'] = "next →";
        $config['prev_link'] = "← previous";
        $this->pagination->initialize($config);
        $data['pagination'] = $this->pagination->create_links();
        
        $this->load->view('templates/header', $data);
        $this->load->view('index', $data);
    }