Separate getting of formatted error messages

[arogachev]

A concept suggested by @xepozz.

$messages = new ErrorMessages();
// index by
$messages->indexByKey();
$messages->indexByParameter();
$messages->indexBy($closure);
// select
$messages->firstErrors();
$messages->firstError();
$messages->all();
// filter errors
$messages->filter($closure);

[roxblnfk]

It looks interesting. Could you add more details?