Fix potential bugs without expected behavior change

- Fix uninitialized variables
- Fix potentially not set variables
- Fix wrong parameter default value
- Fix method scope
- Fix missing return value

mod/dfrn_notify.php

@@ -300,6 +300,7 @@ function dfrn_notify_content(App $a) {
 				break;
 			default:
 				$status = 1;
+				$my_id = '';
 				break;
 		}