Hello.

There may be an issue with the composer.json since PHP version 7.1.12
due to the fix for bug #75287 (see https://bugs.php.net/bug.php?id=75287).

Running from the command line:

composer run --timeout=0 serve

calls the inbuilt web server via this line in the composer.json:
"serve": "php -S 0.0.0.0:8080 -t public public/index.php",

This results in a fatal error as the path taken is now public/public/index.php

due to the router script (public/index.php in the composer.json) now being relative

to document root (public) due to the above fix.

Changing the composer line to:
"serve": "php -S 0.0.0.0:8080 -t public index.php"

corrects the problem for PHP >=7.1.12

The problem is repeatable.

Kevin S