[PHP] Five Server drops "stderr" errors whenever defining arrays from a HTML Form

[itsfirestorm]

Describe the bug Given I use Live Server for almost all of my projects, I got excited when I saw this fork had PHP compatibility, but whenever trying to serve a PHP project with Five Server it refuses to work, if I define any array key from a HTML Form it gives the following error.

stderr: PHP Warning: Undefined array key "key1" in /path/to/file.php on line x

After looking around I couldn't find any issue that could relate this to Five Server, so I deduced it was probably an error on my end, but whenever serving this exact file through XAMPP, it works perfectly, with no issues whatsoever.