get_next_article.php

<?php

if (!function_exists('pr')) {

    function pr()
    {
        array_map(function ($x) {
            echo '<pre>'; print_r($x); echo '</pre>';
        }, func_get_args()); die;
    }
}


if (! function_exists('getNextArticle')) {

    function getNextArticle($category_id, $ignore_offline = false) {

        $articles = OOArticle::getArticlesOfCategory($category_id, $ignore_offline);
        
        $next_article = null;
        $save_next_article = false;
        foreach ($articles as $article) {

            if ($article->getId() != REX_ARTICLE_ID && $next_article == null) {
                $next_article = $article;
            }

            if ($save_next_article) {
                $next_article = $article;
                break;
            }
            
            if ($article->getId() == REX_ARTICLE_ID) {
                $save_next_article = true;
            }
        }

        if ($next_article == null) {
            
            $children = OOCategory::getChildrenById($category_id, $ignore_offline);

            if (count($children) > 0) {
                foreach ($children as $child) {
                    $next_article = getNextArticle($child->getId(), $ignore_offline);

                    if ($next_article instanceof OOArticle) {
                        break;
                    }
                }
            }
        }


        return $next_article;
    }
}

$a = getNextArticle(REX_CATEGORY_ID, true);

pr($a);

?>