MessageCollection::getCommonChatId

public function getCommonChatId(): ?int
{
	$id = null;

	foreach ($this as $message)
	{
		if (isset($id) && $message->getChatId() !== $id)
		{
			return null;
		}

		if (!isset($id))
		{
			$id = $message->getChatId();
		}
	}

	return $id;
}