Add CSS body classes for the parent page on all child pages and the parent page template on of a WordPress site with this body_class filter. Ever need to style all child pages of a parent page in the same way or have you wanted to access every child page of a parent page via css selectors for styling? What about selecting all pages that are descendants of a page which is using a specific template?
Building large websites gets complicated, even in WordPress. Large sites usually mean there are many subpages and sections to the website that may need to be styled similarly. I’ve found it helpful to add a page’s parent page slug to the body class to allow me to alter or target the page or group of pages via css. By default the themes I’ve used have been generous in adding classes to the html body element for easy css selection rules. Things like the post slug, page template, logged in status, page vs post (or custom post type), post id, author… you get the idea. While half the time I don’t need half of this and the other half the time I find myself needing more.
Place this code into your functions.php file and your html body element will have a couple additional classes if they apply. It will have a class delineating the slug for the parent page on all child pages as well as a class delineating the template used by the parent page. This lets me apply styles to a whole sibling-section of a site pretty easily by just targeting the parent-slug on the body. Also adding the template of the parent in case I needed to use that.
Walking through the code here we’re filtering the body_class function is how we are able to add this. We name our own function and give it a $classes parameter. Then throughout our function we can add classes to this $classes array and they will be output with the rest of the body classes. We need to hook into WordPress at the body_class function with add_filter and specify the hook and specify our own function to be called. In this case we grab the page properties of post_parent and the template of that parent. First set the post variable to reference the global scope, and then check to see if the post is a page with is_page. Then if the post object has a value for the parent (post_parent) we add the parent’s name to the classes array. Then we get the _wp_page_template meta data from the parent to find the template it’s using (if there is no template specified, then it returns default). This is added to our classes if it exists and then we return the classes array to the original body_class WP core function.
[cc lang=”php”]
/////////////////////////////////////////////////////////////////////////////////
// Body class adding page-parent
//
function cc_body_class( $classes ) {
global $post;
if ( is_page() ) {
// Has parent / is sub-page
if ( $post->post_parent ) {
# Parent post name/slug
$parent = get_post( $post->post_parent );
$classes[] = ‘parent-slug-‘.$parent->post_name;
// Parent template name
$parent_template = get_post_meta( $parent->ID, ‘_wp_page_template’, true);
if ( !empty($parent_template) )
$classes[] = ‘parent-template-‘.sanitize_html_class( str_replace( ‘.’, ‘-‘, $parent_template ), ” );
}
}
return $classes;
}
add_filter( ‘body_class’, ‘cc_body_class’ );
[/cc]
There are many more classes we can add to the body_class and like I said, sometimes you need more than what’s already provided and sometimes you need nothing. It all depends on the theme you’re using, what it provides and what your specific site and design require. What other classes have you wanted to see here? How have you filtered body_class to fit your site’s needs?
Building large websites gets complicated, even in WordPress. Large sites usually mean there are many subpages and sections to the website that may need to be styled similarly. I’ve found it helpful to add a page’s parent page slug to the body class to allow me to alter or target the page or group of pages via css. By default the themes I’ve used have been generous in adding classes to the html body element for easy css selection rules. Things like the post slug, page template, logged in status, page vs post (or custom post type), post id, author… you get the idea. While half the time I don’t need half of this and the other half the time I find myself needing more.
Walking through the code here we’re filtering the 
