WP pagination for single post to show in multiple pages

// Wp pagination for single post to show multiple page
// 1) The following filter for the next page and previous page option

function wp_link_pages_args_prevnext_add($args)
{
    global $page, $numpages, $more, $pagenow;

    if (!$args['next_or_number'] == 'next_and_number')
        return $args; # exit early

    $args['next_or_number'] = 'number'; # keep numbering for the main part
    if (!$more)
        return $args; # exit early

    if($page-1) # there is a previous page
        $args['before'] .= _wp_link_page($page-1)
            . $args['link_before']. $args['previouspagelink'] . $args['link_after'] . '</a>'
        ;

    if ($page<$numpages) # there is a next page
        $args['after'] = _wp_link_page($page+1)
            . $args['link_before'] . ' ' . $args['nextpagelink'] . $args['link_after'] . '</a>'
            . $args['after']
        ;

    return $args;
}

add_filter('wp_link_pages_args', 'wp_link_pages_args_prevnext_add');

//After the_content() should attach the following pagination function

wp_link_pages(array(
  'before'      => '<div class="page-links">',
    'after'       => '</div>',
));