PropertyRepository::save

public function save(BaseEntity ...$entities): Result
{
	$result = new Result();

	/** @var BitrixCatalogv2BaseIblockElementEntity $parentEntity */
	$parentEntity = null;
	$props = [];

	/** @var BitrixCatalogv2PropertyProperty $property */
	foreach ($entities as $property)
	{
		if ($parentEntity && $parentEntity !== $property->getParent())
		{
			$result->addError(new Error('Saving should only be done with properties of a common parent.'));
		}

		if ($parentEntity === null)
		{
			$parentEntity = $property->getParent();
		}

		$valueCollection = $property->getPropertyValueCollection();

		$props[$property->getId()] = $valueCollection->toArray();

		if ($property->getPropertyType() === PropertyTable::TYPE_FILE)
		{
			foreach ($props[$property->getId()] as $id => $prop)
			{
				if (is_numeric($id))
				{
					$props[$property->getId()][$id] = CIBlock::makeFilePropArray(
						$prop,
						$prop['VALUE'] === '',
						$prop['DESCRIPTION'],
						['allow_file_id' => true]
					);
				}
			}

			foreach ($valueCollection->getRemovedItems() as $removed)
			{
				if ($removed->isNew())
				{
					continue;
				}

				$fieldsToDelete = CIBlock::makeFilePropArray($removed->getFields(), true);
				$props[$property->getId()][$removed->getId()] = $fieldsToDelete;
			}
		}
	}

	if (!$parentEntity)
	{
		$result->addError(new Error('Parent entity not found while saving properties.'));
	}

	if (!($parentEntity instanceof BaseIblockElementEntity))
	{
		$result->addError(new Error(sprintf(
			'Parent entity of property must be an instance of {%s}.',
			BaseIblockElementEntity::class
		)));
	}

	if (!empty($props) && $result->isSuccess())
	{
		$element = new CIBlockElement();
		$res = $element->update($parentEntity->getId(), [
			'PROPERTY_VALUES' => $props,
		]);
		if (!$res)
		{
			$result->addError(new Error($element->LAST_ERROR));
		}
	}

	return $result;
}