Enhance PHP workers are containerised but this is implemented at a kernel level with the PHP SAPI as PID 1 so there is almost zero overhead for this. You
ssh directly into the customer's website container, just like you can on legacy panels.
There is always one PHP worker per website but this isn't related to the PHP containerisation. In the future we may be able to complete shut down the PHP SAPI for idle websites. If we implement this, it will be a platform setting.