【WordPress】投稿画面でタグを全表示し、クリックで選択可能にする

<?php

add_action('load-post.php', 'select_post_tags');
add_action('load-post-new.php', 'select_post_tags');
function select_post_tags()
{
    $all_tags = get_tags([
        'hide_empty' => false,
        'fields' => 'names'
    ]);
    if (empty($all_tags)) {
        return;
    }

    $current_post_id = filter_input(INPUT_GET, 'post', FILTER_VALIDATE_INT);
    $current_post_tags = [];
    if ($current_post_id) {
        $current_post_tags = get_the_tags($current_post_id) ?: [];
        if (!empty($current_post_tags)) {
            $current_post_tags = array_column($current_post_tags, 'name');
        }
    }

    $css          = 'style="list-style:outside disc; cursor:pointer;"';
    $selected_css = 'style="list-style:outside disc; cursor:pointer; font-weight:bold; color:red"';
    $js           = "onmouseover=\"this.style.textDecoration='underline'\" onmouseout=\"this.style.textDecoration='none'\"";

    $html_tag_list = '<ul id="select-post-tags" style="padding-left:1em; word-wrap:break-word;">';
    foreach ($all_tags as $tag) {
        $style = (array_search($tag, $current_post_tags) === false) ? $css : $selected_css;
        $html_tag_list .= "<li {$style} {$js}>" . esc_html($tag) . "</li>";
    }
    $html_tag_list .= '</ul>';

    add_action('admin_print_footer_scripts', function () use ($html_tag_list) {
?>
        <script type="text/javascript">
            (function($){
                'use strict';
                $('#post_tag').before(`<?= $html_tag_list; ?>`);

                $('#select-post-tags li').on('click', function (e) {
                    const $item = $(this);

                    $item.css({'font-weight': 'bold', 'color': 'red'});
                    $('#new-tag-post_tag').val($item.text() + ', ');
                    $('.button.tagadd').trigger('click');

                    return false;
                });
            })(jQuery);
        </script>
<?php
    });
}