Facebook changed the permissions.
You can not get all Facebook friend.
You can only get the friends which are using your application.
From the Facebook documents :
https://developers.facebook.com/docs/facebook-login/permissions/v2.4
user_friends
Provides access the list of friends that also use your app. These
friends can be found on the friends edge on the user object.
In order for a person to show up in one person's friend list, both
people must have decided to share their list of friends with your app
and not disabled that permission during login. Also both friends must
have been asked for user_friends during the login process. Review
Your app may use this permission without review from Facebook. Common
Usage
Use the list of friends to create a social experience in your app.
Also described in the
read_custom_friendlists
Provides access to the names of custom lists a person has created to
organize their friends. This is useful for rendering an audience
selector when someone is publishing stories to Facebook from your app.
This permission does not give access to a list of person's friends. If
you want to access a person's friends who also use your app, you
should use the user_friends permission.
This permission will also not help you invite a person's friends to
use your app. To learn more about how to invite friends to an app,
please see our FAQs.
This permission also does not give the list of friends who are part of
a friendlist. It only gives access to the names of the lists.
This permission was called read_friendlists before v2.3