Issue with sql.safe_mode

Hello.

I will try to describe step by step the issue so you can understand better:

1. I have four wordpress websites, one of them is https.
2. Three of them use the same theme. One uses a new different theme, it is under http.
3. When I activate the PHP function sql.safe_mode in my server, the https website and the new different theme http website go down, error “error database connection”. The remaining two http websites continue loading well.

As I wish to improve PHP security, I would prefer to leave sql.safe_mode activated. Is there any way to check why those two websites (one https and the new theme website http) go down when I activate sql.safe_mode?

Any advice is welcome! ??