This little snippet will take all the categories assigned to a post and add them to the body_class "sgl-cat-{category-name}".
add_filter('body_class','add_category_to_single');
function add_category_to_single($classes, $class) {
if (is_single() ) {
global $post;
foreach((get_the_category($post->ID)) as $category) {
$classes[] = 'sgl-cat-'.$category->category_nicename;
}
}
return $classes;
}
Great, but you need one correction or the above code will give a fatal error. The hook should have:
add_filter(‘body_class’,’add_category_to_single’,10,2) since you pass in 2 parameters.