This uses Twitter Bootstrap 4.1 classes for CodeIgniter pagination. Drop this file into application/config.

pagination.php

<?php 
/**
 * Pagination Config
 * 
 * Just applying codeigniter's standard pagination config with twitter 
 * bootstrap 4.1 stylings
 * 
 * @license		http://www.apache.org/licenses/LICENSE-2.0  Apache License 2.0
 * @author		Ali Asjad
 * @link		http://codeigniter.com/user_guide/libraries/pagination.html
 * @email		mianaliasjad@gmail.com
 * 
 * @file		pagination.php
 * @date		07/04/2018
 */
 
// --------------------------------------------------------------------------

if ( ! defined('BASEPATH')) exit('No direct script access allowed');

$config['full_tag_open'] 	= '<nav aria-label="Page navigation" class="pagination-nav"><ul class="pagination">';
$config['full_tag_close'] 	= '</ul></nav>';
$config['num_tag_open'] 	= '<li class="page-item">';
$config['num_tag_close'] 	= '</li>';
$config['cur_tag_open'] 	= '<li class="page-item active"><span class="page-link">';
$config['cur_tag_close'] 	= '<span class="sr-only">(current)</span></span></li>';
$config['next_tag_open'] 	= '<li class="page-item">';
$config['next_tagl_close'] 	= '<span aria-hidden="true">&raquo;</span></li>';
$config['prev_tag_open'] 	= '<li class="page-item">';
$config['prev_tagl_close'] 	= '</li>';
$config['first_tag_open'] 	= '<li class="page-item d-none">';
$config['first_tagl_close'] = '</span></li>';
$config['last_tag_open'] 	= '<li class="page-item d-none">';
$config['last_tagl_close'] 	= '</li>';
$config['next_link'] = 'Next';
$config['prev_link'] = 'Previous';
$config['use_page_numbers'] = TRUE;
 
 
 // --------------------------------------------------------------------------
/* End of file pagination.php */
/* Location: /application/config/pagination.php */
/* After pasting this file then goto the controller where you are creating pagination and then paste lines given below */
/* $config=[
				'base_url' => your base url,
				'per_page' => 5,
				'total_rows' => your total rows number
        ];
$config['attributes'] = array('class' => 'page-link'); //it is necessary   
$this->pagination->initialize($config);

Now to show pagination just call
echo $this->pagination->create_links();  */