Custom CSS and JS with WordPress meta box's

Добавляем кастомные метабоксы для стилей и скриптов под постами и страницами (найдено было тут):

add_action('admin_menu', 'custom_css_hooks');
add_action('save_post', 'save_custom_css');
add_action('wp_head','insert_custom_css');
function custom_css_hooks() {
    add_meta_box('custom_css', 'Custom CSS', 'custom_css_input', 'post', 'normal', 'high');
    add_meta_box('custom_css', 'Custom CSS', 'custom_css_input', 'page', 'normal', 'high');
}
function custom_css_input() {
    global $post;
    echo '<input type="hidden" name="custom_css_noncename" id="custom_css_noncename" value="'.wp_create_nonce('custom-css').'" />';
    echo '<textarea name="custom_css" id="custom_css" rows="5" cols="30" style="width:100%;">'.get_post_meta($post->ID,'_custom_css',true).'</textarea>';
}
function save_custom_css($post_id) {
    if (!wp_verify_nonce($_POST['custom_css_noncename'], 'custom-css')) return $post_id;
    if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) return $post_id;
    $custom_css = $_POST['custom_css'];
    update_post_meta($post_id, '_custom_css', $custom_css);
}
function insert_custom_css() {
    if (is_page() || is_single()) {
        if (have_posts()) : while (have_posts()) : the_post();
            echo '<style type="text/css">'.get_post_meta(get_the_ID(), '_custom_css', true).'</style>';
        endwhile; endif;
        rewind_posts();
    }
}

add_action('admin_menu', 'custom_js_hooks');
add_action('save_post', 'save_custom_js');
add_action('wp_footer','insert_custom_js');
function custom_js_hooks() {
    add_meta_box('custom_js', 'Custom JS', 'custom_js_input', 'post', 'normal', 'high');
    add_meta_box('custom_js', 'Custom JS', 'custom_js_input', 'page', 'normal', 'high');
}
function custom_js_input() {
    global $post;
    echo '<input type="hidden" name="custom_js_noncename" id="custom_js_noncename" value="'.wp_create_nonce('custom-js').'" />';
    echo '<textarea name="custom_js" id="custom_js" rows="5" cols="30" style="width:100%;">'.get_post_meta($post->ID,'_custom_js',true).'</textarea>';
}
function save_custom_js($post_id) {
    if (!wp_verify_nonce($_POST['custom_js_noncename'], 'custom-js')) return $post_id;
    if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) return $post_id;
    $custom_js = $_POST['custom_js'];
    update_post_meta($post_id, '_custom_js', $custom_js);
}
function insert_custom_js() {
    if (is_page() || is_single()) {
        if (have_posts()) : while (have_posts()) : the_post();
            echo '<script>'.get_post_meta(get_the_ID(), '_custom_js', true).'</script>';
        endwhile; endif;
        rewind_posts();
    }
}