See bug : #3418311, I have the same problem, but in the Git (20111004-022002), not in 3.4.5
On older versions of phpMyAdmin (including 3.4.5), at the end of the SQL dump, it adds the alter table to add the foreign keys, like so :
ALTER TABLE `usersPermissions`
ADD CONSTRAINT `usersPermissions_ibfk_2` FOREIGN KEY (`user`) REFERENCES `users` (`identifier`) ON DELETE CASCADE,
ADD CONSTRAINT `usersPermissions_ibfk_3` FOREIGN KEY (`permission`) REFERENCES `permissions` (`identifier`) ON DELETE CASCADE;
I have found that in the few latest Git snapshot, the export doesn't export the foreign keys anymore. I have tested with different tables/schemas.