topic.php

См. документацию.

<?php
 
namespace Bitrix\Forum\Controller;
 
use Bitrix\Main;
use Bitrix\Forum;
 
class Topic extends Main\Engine\Controller
{
    public function headAction($topicId)
    {
        if (($topic = Forum\Topic::getById($topicId)) !== null)
        {
            global $USER;
            $user = Forum\User::getById($USER->GetID());
            if ($user->canReadTopic($topic))
            {
                return $topic->getData();
            }
        }
        return null;
    }
}