zendframework/zf2 — pull request #2936 by odnanref (2012-11-11 12:33:50+00:00)
Title: Make case insensitive ssl config option to be more consistent with Mail\...

...Transport\SmtpOptions

php -r 'print ("ssl" === "SSL" ? "OK\n" : "Nein\n");'

This way it doesn't matter how you write it, you'll have the same result for the config.