There are many reasons for the invalidation of the invitation code, such as the expiration of the invitation code or the repeated use of the same invitation code for many times.

Some forums, mailboxes, blogs and special IDs need a special pass when registering-that is, the invitation code is equivalent to entering the registration code when using a software. It's the same as an invitation in real life. Only when you receive the invitation code can you register your account. When the forum is open to invite registration, the invitation code becomes a necessary condition for registering the forum. If you want to register an ID, you must get a valid invitation code. At this time, the general registration function.