Add JSON as web service protocol

1. From admin/settings.php?section=webservicesoverview setup web services either as one system or users accessing a web service. 2. Enable JSON protocol (from step 2 on this screen) 3. Ensure function 'moodle_user_get_users_by_id' is available to the web service user (step 6 or 4). 3. Access the web service test client: admin/webservice/testclient.php 4. Select json protocol and function 'moodle_user_get_users_by_id'. 5. Select the authentication method that matches the web service setup undertaken in step 1. 6.Submit the form and on the following screen enter either the token or login/password for the web service user. Enter some valid user ids for the web service to return. 7. If successful copy and paste the resulting JSON (minus surrounding single quotes). 8. Test JSON for validity e.g. at http://jsonlint.com/