Add category to body class

Question

I want to add the currenty category to the body class.

How do I need to modify my current code, to add also the current category as a body class to the is_singular( 'knowledgebase' ) section?

My current code looks like this:

function add_body_class( $classes ) {

    global $pakb;

    if( is_page( $pakb->get( 'kb_page' ) ) && ! is_null(  $pakb->get( 'kb_page' ) ) ) {
        $classes[] = 'pakb-main';
    } elseif ( is_tax( 'knowledgebase_category' ) ) {
        $classes[] = 'pakb-category';
    } elseif ( is_singular( 'knowledgebase' ) ) {
        $classes[] = 'pakb-single';
    }

    return $classes;

}

Answer 1

This late in the process you should be able to rely on context set up, even outside of loop.

On top of my head something like this should work:

$categories = wp_get_post_categories( get_the_ID(), [ 'fields' => 'names' ] );

Answer 2

Here I don't understand what is global $pakb.

But extending to Rarst answer :

add_filter('body_class', 'add_body_class');

function add_body_class($classes) {
    global $pakb;
    global $post;

    if( is_page( $pakb->get( 'kb_page' ) ) && ! is_null(  $pakb->get( 'kb_page' ) ) ) {
        $classes[] = 'pakb-main';
    } elseif ( is_singular( 'knowledgebase' ) ) {
        // getting all category name related to this post
        $categories = wp_get_post_categories( $post->ID, [ 'fields' => 'names' ] );

        $classes[] = $categories;
    }

    return $classes;

return $classes;
}