Wordpress 5.7 Bootstrap 5.0 pagination (with custom WP_Query() and global $wp_query support)

wp-bootstrap5.0-pagination.php

<?php
/**
 * @param WP_Query|null $wp_query
 * @param bool $echo
 * @param array $params
 *
 * @return string|null
 * 
 * Using Bootstrap 4? see https://gist.github.com/mtx-z/f95af6cc6fb562eb1a1540ca715ed928
 * 
 * Accepts a WP_Query instance to build pagination (for custom wp_query()),
 * or nothing to use the current global $wp_query (eg: taxonomy term page)
 * - Tested on WP 5.7.1
 * - Tested with Bootstrap 5.0 (https://getbootstrap.com/docs/5.0/components/pagination/)
 * - Tested on Sage 9.0.9
 *
 * INSTALLATION:
 * add this file content to your theme function.php or equivalent
 *
 * USAGE:
 *     <?php echo bootstrap_pagination(); ?> //uses global $wp_query
 * or with custom WP_Query():
 *     <?php
 *      $query = new \WP_Query($args);
 *       ... while(have_posts()), $query->posts stuff ... endwhile() ...
 *       echo bootstrap_pagination($query);
 *     ?>
 */
function bootstrap_pagination( \WP_Query $wp_query = null, $echo = true, $params = [] ) {
    if ( null === $wp_query ) {
        global $wp_query;
    }

    $add_args = [];

    //add query (GET) parameters to generated page URLs
    /*if (isset($_GET[ 'sort' ])) {
        $add_args[ 'sort' ] = (string)$_GET[ 'sort' ];
    }*/

    $pages = paginate_links( array_merge( [
            'base'         => str_replace( 999999999, '%#%', esc_url( get_pagenum_link( 999999999 ) ) ),
            'format'       => '?paged=%#%',
            'current'      => max( 1, get_query_var( 'paged' ) ),
            'total'        => $wp_query->max_num_pages,
            'type'         => 'array',
            'show_all'     => false,
            'end_size'     => 3,
            'mid_size'     => 1,
            'prev_next'    => true,
            'prev_text'    => __( '« Prev' ),
            'next_text'    => __( 'Next »' ),
            'add_args'     => $add_args,
            'add_fragment' => ''
        ], $params )
    );

    if ( is_array( $pages ) ) {
        //$current_page = ( get_query_var( 'paged' ) == 0 ) ? 1 : get_query_var( 'paged' );
        $pagination = '<nav aria-label="Page navigation"><ul class="pagination">';

        foreach ( $pages as $page ) {
            $pagination .= '<li class="page-item' . (strpos($page, 'current') !== false ? ' active' : '') . '"> ' . str_replace('page-numbers', 'page-link', $page) . '</li>';
        }

        $pagination .= '</ul></nav>';

        if ( $echo ) {
            echo $pagination;
        } else {
            return $pagination;
        }
    }

    return null;
}

/**
 * Notes:
 * AJAX:
 * - When used with wp_ajax (generate pagination HTML from ajax) you'll need to provide base URL (or it'll be admin-ajax URL)
 * - Example for a term page: bootstrap_pagination( $query, false, ['base' => get_term_link($term) . '?paged=%#%'] )
 *
 * Images as next/prev:
 * - You can use image as next/prev buttons
 * - Example: 'prev_text' => '<img src="' . get_stylesheet_directory_uri() . '/assets/images/prev-arrow.svg">',
 *
 * Add query parameters to page URLs
 * - If you need custom URL parameters on your page URLS, use the "add_args" attribute
 * - Example (before paginate_links() call):
 * $arg = [];
 * if (isset($_GET[ 'sort' ])) {
 *  $args[ 'sort' ] = (string)$_GET[ 'sort' ];
 * }
 * ...
 * 'add_args'     => $args,
 */