ZP-322 #comment use "old" method to check if decode() is called statically, as usage of is_a() causes E_STRICT messages on 5.0.0 until 5.3.0 #time 20m

git-svn-id: https://z-push.org/svn/z-push/trunk@1612 b7dd7b3b-3a3c-0410-9da9-bee62a6cc5b5