PHP local server Invalid request (Unexpected EOF)

This could be related to Chrome specifically and its network prediction feature. So try to disable that feature first. That's why it works for you in Incognito mode, because probably it's disabled in that mode.

You can find this option in Chrome Settings and click on 'Show advanced settings'. Should be there in Privacy section.

This is a known bug.

From https://bugs.php.net/bug.php?id=60471:

[2011-12-08 15:01 UTC] lolautruche at gmail dot com Description:
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From time to time, built-in server with router script logs this kind of stuff :

[Thu Dec 8 13:39:29 2011] 127.0.0.1:50358 Invalid request (Unexpected EOF)

This happens quite randomly, whatever the script has a close tag or not, whatever it has a blank line after close tag or not.

And the explanation:

[2012-02-23 18:45 UTC] michal dot pipa dot xsolve at gmail dot com
...
Chromium has feature called "Predict network actions to improve page load performance" and its enabled by default. It works this way, that if HTML page has links to some resources, than Chromium opens about 10 TCP connections in advance. And then if browser has less than 10 resources to fetch, unused connections times out after 10 seconds. And this (empty payload) causes PHP server to display "Invalid request (unexpected EOF)" message.

It is a harmless error from the PHP built-in server.