CLearnLessonTree::BuildTreeRecursive

protected function BuildTreeRecursive ($rootLessonId, $arOrder, $arFilter, $depth = 0, $parentChapterId = NULL, $arSelectFields, $arRootPath)
{
	$oPath = new CLearnPath();
	$arLessons = array();

	$CDBResult = CLearnLesson::GetListOfImmediateChilds($rootLessonId, $arOrder, $arFilter, $arSelectFields);
	while (($arData = $CDBResult->Fetch()) !== false)
	{
		// Skip lessons that are already in tree (prevent cycling)
		if ( in_array($arData['LESSON_ID'], $this->arLessonsInTree) )
			continue;

		// Skip lessons prohibited for publishing
		if (in_array( (int) $arData['LESSON_ID'], $this->arPublishProhibitedLessons, true))
			continue;

		// Path as array for current LESSON_ID
		$arCurrentLessonPath = $arRootPath;
		$arCurrentLessonPath[] = (int) $arData['LESSON_ID'];
		$oPath->SetPathFromArray($arCurrentLessonPath);
		$strUrlencodedCurrentLessonPath = $oPath->ExportUrlencoded();


		// Register lesson
		$this->arLessonsInTree[] = $arData['LESSON_ID'];
		$this->arLessonsAsList[] = array_merge(
			$arData, 
			array(
				'#DEPTH_IN_TREE' => $depth,
				'#LESSON_PATH'   => $strUrlencodedCurrentLessonPath
			)
		);

		// hack: we don't know yet, what index name must be for element in array.
		// And we must preserve order in array elements (for compatibility).
		// But we will know index name after BuildTreeRecursive will be called, which
		// adds to array new elements. So create bother elements, and after remove unneeded.
		$this->arLessonsAsListOldMode['LE' . $arData['LESSON_ID']] = array();
		$this->arLessonsAsListOldMode['CH' . $arData['LESSON_ID']] = array();

		$item = $arData;
		$item['#childs'] = array();
		$lessonType_oldDataModel = 'LE';

		if ($arData['IS_CHILDS'])
		{
			$lessonType_oldDataModel = 'CH';
			$item['#childs'] = $this->BuildTreeRecursive (
				$arData['LESSON_ID'], 
				$arOrder, 
				$arFilter, 
				$depth + 1, 
				$arData['LESSON_ID'], 
				$arSelectFields,
				$arCurrentLessonPath
			);
			
			// It still can be zero childs due to $arFilter, publish prohibition or prevent cycling instead of non-zero $arData['IS_CHILDS']
			if (count($item['#childs']) == 0)
				$lessonType_oldDataModel = 'LE';
		}

		// remove unneeded element caused by hack above			
		if ($lessonType_oldDataModel === 'LE')
			unset($this->arLessonsAsListOldMode['CH' . $arData['LESSON_ID']]);
		else
			unset($this->arLessonsAsListOldMode['LE' . $arData['LESSON_ID']]);
		
		$this->arLessonsAsListOldMode[$lessonType_oldDataModel . $arData['LESSON_ID']] = array_merge(
			$arData, 
			array(
				'ID'           => $arData['LESSON_ID'],
				'CHAPTER_ID'   => $parentChapterId,
				'SORT'         => $arData['EDGE_SORT'],
				'TYPE'         => $lessonType_oldDataModel,
				'DEPTH_LEVEL'  => $depth + 1,
				'#LESSON_PATH' => $strUrlencodedCurrentLessonPath
				)
			);

		$arLessons[] = $item;
	}

	return ($arLessons);
}