如何在facebook中使first_name + last_name唯一？

Since username is no longer available in facebook callback url field , im thinking using first_name+last_name But i dont know if this is unique in facebook so i can use it as username in my website . If not how can i make it unique ?

thanks .

this what im getting

  $user_profile = $facebook->api('/me?fields=id,name,email,gender,picture');

There is one field that you should user to identify returning users, it is the "id" field. Everything else is not unique. You even ask for it in the API call, it will be in the result. If you want to auto-create a username, use the first_name and last_name fields, but let the user change it and check if the username exists already.