viewed.php

См. документацию.

<?php
namespace Bitrix\Catalog\Product;
 
use Bitrix\Main,
    Bitrix\Iblock,
    Bitrix\Catalog;

class Viewed
{
    public static function getParentSection($sectionId, $depth)
    {
        $sectionId = (int)$sectionId;
        $depth = (int)$depth;
        if ($sectionId <= 0 || $depth <= 0)
            return null;
        $section = Iblock\SectionTable::getList(array(
            'select' => array('ID', 'IBLOCK_ID', 'LEFT_MARGIN', 'RIGHT_MARGIN', 'DEPTH_LEVEL'),
            'filter' => array('=ID' => $sectionId)
        ))->fetch();
        if (empty($section))
            return null;
        $section['DEPTH_LEVEL'] = (int)$section['DEPTH_LEVEL'];
        if ($section['DEPTH_LEVEL'] < $depth)
            return null;
        if ($section['DEPTH_LEVEL'] == $depth)
            return (int)$section['ID'];
 
        $parentSection = Iblock\SectionTable::getList(array(
            'select' => array('ID'),
            'filter' => array(
                '=IBLOCK_ID' => $section['IBLOCK_ID'],
                '<=LEFT_MARGIN' => $section['LEFT_MARGIN'],
                '>=RIGHT_MARGIN' => $section['RIGHT_MARGIN'],
                '=DEPTH_LEVEL' => $depth
            )
        ))->fetch();
        if (!empty($parentSection))
            return (int)$parentSection['ID'];
 
        return null;
    }
}