@yanggh No it's not. I was looking into this, having different version of php.ini on same system is not a feasible solution. A way to around it could be as mentioned in this post. . Another way for this could be deploying those sites in docker containers and then having a load balancer with a local DNS to direct all the ingress requests to their respective containers.
But none of the above method have been tested by me. So I really can't suggest a solution right now.