And probably add logic to allow the web server to restart the process if it should fail/crash and maybe recycle it ever Nth hour. Bad C++ code could easily make your process crash.
Apache's mod_fastcgi/mod_fcgid used to try and manage its own FastCGI processes, but the result was rather brittle. It was also a non-starter when the FastCGI processes were on a different machine for load balancing purposes.
It's much simpler to use an independent monitoring program to manage your processes than to rely on the web server. Modern init systems can do this for you, or you can use tools like monit. Docker will probably work, too. Node has PM2. PHP has FPM, which can automatically recycle processes on a preconfigured schedule. Not that they need to be recycled, because PHP is very stable these days, but it's just a one-liner in a config file if you need it.
It's much simpler to use an independent monitoring program to manage your processes than to rely on the web server. Modern init systems can do this for you, or you can use tools like monit. Docker will probably work, too. Node has PM2. PHP has FPM, which can automatically recycle processes on a preconfigured schedule. Not that they need to be recycled, because PHP is very stable these days, but it's just a one-liner in a config file if you need it.