Can I merge results on 2 indices?

I have 2 indices in ElasticSearch with different mapping types (they have some different attributes). I am using Yii2 framework on php to search on web.

Question: Can I search over 2 indices (if it is possible) and merge results in one sorted by date for example? If yes, where to read about this? Moreover, in Yii2 we create .php files, each one represents one indice with one class. So, I have to use that 2 classes to merge, I think I can not just write long ES command in curl.

Here is question with demo code