invite system

i am using phpbb3 on forum. can anyone tell me if there is anything that i can use to make it invite system on forum ? invite code stuff... pls let me know if there is anything i can use. thanks

By invite system you mean that users can register only by invites? If yes, I'm sorry, you can't. But you can try a simple trick: Go to Administration Panel => Users & Groups => Users => Users options => Members => New accounts activation : Admin. Then create a field that is obligatory on registration. Users & Groups => Users => Profiles => => and you can make an code field and when you'll going to Users & Groups => Users => Inactive users, you'll check if code is correct and activate user if you want.