[WordPress] custom template selon custom category

// Arthur - custom template selon custom category
add_filter('single_template','check_for_category_single_template');
function check_for_category_single_template($t) {
    $cats = get_the_terms(get_the_ID(),'project-type');
    foreach((array)$cats as $cat) {
        if (file_exists(get_stylesheet_directory().'/single-'.$cat->slug.'.php'))
            return get_stylesheet_directory().'/single-'.$cat->slug.'.php';
        if ($cat->parent) {
            $cat = get_the_category_by_ID($cat->parent);
            if (file_exists(get_stylesheet_directory().'/single-'.$cat->slug.'.php'))
                return get_stylesheet_directory().'/single-'.$cat->slug.'.php';
        }
    }
    return $t;
}