## mark a section (Learn more)

<?php function mytheme_body_class($classes) { global $post; if (is_single()) { $categories = get_the_category($post->ID); if (isset($categories) && is_array($categories)) { foreach ($categories as $category) { $classes[] = $category->slug; } } } return $classes; } add_filter('body_class', 'mytheme_body_class'); ?>

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