I came across this library and thought I'd give it a try. The speed improvements are amazing but I'm getting "Script did not return a valid HTTP response. Maybe it has called exit() prematurely?" from time to time, as I am browsing through the different pages.

I'm running
./vendor/bin/ppm start --static-directory=public/ --app-env=prod --logging=0 --debug=0
on a symfony 4.4 application, on my local machine (ubuntu 20).

When I'm running with debug and logging, it doesn't really help, here is a sample output:

[23/Feb/2022:08:11:52 +0200] 127.0.0.1 - - "GET /admin/ajax/taxons/leafs HTTP/1.1" 200 21812 "http://localhost:8080/admin/products/15950/edit"
[23/Feb/2022:08:11:55 +0200] 127.0.0.1 - - "GET /admin/products/ HTTP/1.1" 200 112551 "http://localhost:8080/admin/products/"
Script did not return a valid HTTP response. Maybe it has called exit() prematurely?

I searched for relevant issues, but didn't really find an answer. It's got something to do with the client closing the connection? Why would that happen?