If fphttpapp web app is running in same machine as Apache web server, it is possible as long as both listen on different port.
Benefit of deploying fphttpapp is less software layer, requests come directly to web app. So there are possible performance benefit depending on how you develop web app. This is not the case with fastcgi/cgi web app as requests are received by Apache and then pass to mod_fcgid/mod_proxy_fcgi/mod_cgi module then to web app.
The benefit using fastcgi/cgi with capable web server such Apache is that many security issues/attacks may already be handled by Apache so less possible attacks to worry. this is not the case when deploying fphttpapp standalone.