Integrating MULTIPLE WordPress sites with another website

I’m trying to integrate two instance of WordPress sites into another website but I face a problem where I’m seeing posts from site #1 in site #2’s place. I used the codes provided here.

After some troubleshooting, I realise the problem lies in the database connection that it’s calling. Would there be a way to terminate all WP calls & variables from the site #1 before calling site #2?