使用PHP从mysql获取数据到JSON

I am using the following PHP code to fetch some data from my database. It contains chats and messages between users in those chats. I want to return the information of both users plus the messages they exchanged. My test data has two chats with ID's 1 and 2. There are two messages, both in chat 1, however for some reason they are returned for both chats 1 and 2. I'm not sure what the problem in my code is. I am using the following PHP code to fetch some