I got really confused by this error message:

 4 | ERROR | CASE statements must not be defined using curly braces | | (PSR2.ControlStructures.SwitchDeclaration.WrongOpenercase) 

In the end I narrowed it down to the problem being usage of ; isntead of :. Frankly I've never known this was even possible, but it is mentioned in the PHP manual:

It's possible to use a semicolon instead of a colon after a case

This can be reproduced with this code:

<?php switch ($foo) { case 1; }

In PSR2 there is no mention if semicolon is allowed in this place so I guess the correct resolution is not to show any errors (certainly not this one).