Web services returning user preferences is too strict on type

Enrol several users to one course as students. As admin: enable "Mobile services": Administration ► Mobile app ► Mobile settings In Plugins ► Web services ► Manage tokens: Create a Token for one of the course users. In the database table user_preferences created a new entry for the user you created the token. The user_preference name should be something including special characters like pipe "my|preference|#|&%name" for example Next, you can do a CURL REST call simulating a WS client. You need to replace the wstoken, courseid and the URL of your moodle instance. curl 'http://localhost/m/stable_master/webservice/rest/server.php?moodlewsrestformat=json' --data 'courseid=8&wsfunction=core_enrol_get_enrolled_users&wstoken=739efbfeecb19bc787b6cb5f88c6cfdc' | python -m "json.tool" Confirm that you receive all the users correctly and in the user who did the request check that you see a preferences field including the preference with the special characters you created Now, call the WS core_user_get_users_by_field passing as parameters: field=id and values [0] =userid (userid should be the id of the user you created the token for). curl 'http://localhost/m/stable_master/webservice/rest/server.php?moodlewsrestformat=json' --data 'wsfunction=core_user_get_users_by_field&field=id&values [0] =138&wstoken=12a2a65aeea2a177055e233f9e303218' | python -m "json.tool" Check that you receive the user preference with the special characters Change the function core_calendar_user_preferences() in calendar/lib.php to define some new custom preferences. $preferences[ 'my|preference|#|&%name' ] = array( 'type' => PARAM_INT, 'choices' => range( 1 , 20 )); $preferences[ 'preference2' ] = array( 'type' => PARAM_INT, 'choices' => range( 1 , 20 )); Clear all caches Finally, using a wstoken generated for an admin you can use the following client: https://github.com/moodlehq/sample-ws-clients/blob/master/PHP-REST/client.php for creating new users. Please, edit the line #44 to change the preference name to the ones you added in step 9. The values will also have to be integers between 1 and 20. Once the users are created, you can use the same script for updating them changing the preference value to a different (but still valid) one. In this case you need to change the script to include the user id and to point to the core_user_update_users WS Once the script finishes, please check that the preference name was updated correctly in the database