laravel/framework — pull request #4010 by eusonlito (2014-03-28 09:50:50+00:00)
Title: Added exception when key named "flash" is used to store flash content in to Session

I think that is good to developers to know what vars are reserved when they are storing data into session.

Also, I think that this reserved var should be documented at http://laravel.com/docs/session