// 在分类页面中获取当前分类别名
$category = get_queried_object();
$category_slug = $category->slug;

// 通过分类ID获取别名
$category_id = 5;
$category_slug = get_category($category_id)->slug;

// 在文章页面中获取所属分类别名
$categories = get_the_category();
$first_category_slug = $categories【0】->slug;

// 在category.php或archive.php中
$current_category = get_queried_object();
if ($current_category->slug == 'news') {
    echo '
';
    // 新闻分类特有内容
} else {
    echo '
';
}

// 使用wp_cache_get优化性能
$category_slug = wp_cache_get('category_slug_'.$category_id);
if (false === $category_slug) {
    $category_slug = get_category($category_id)->slug;
    wp_cache_set('category_slug_'.$category_id, $category_slug);
}