opcache doessn't cache user data. it's for caching bytecode in memory as long as the php script/server is running

i'd like to see a comparison against a firecracker vm and a docker container

Hi, on kraft.cloud we use FC, along with a custom controller and very specialized VMs (unikernels) to have extremely efficient deployments (eg, millisecond cold starts). For a PHP web server, for instance, we can cold start things in about 30ms (https://docs.kraft.cloud/guides/php/). It's also possible to run wasm workloads/blobs (e.g., https://docs.kraft.cloud/guides/wazero/).

The builds are based on Dockerfiles, but for deployment we transparently convert that to unikernels.