create custom field in sugarcrm database and get that value using REST

Hi

I just created a custom field in in database(in user table, i don't know it is good way or not), now i want to get the custom field value using REST api,all value are retrieving except my custom field. Below is my rest api params

$get_entries_parameters = array(

         'session' => $session_id,

         'module_name' => 'Users',

         'ids' => array('1'),

         'select_fields' => array(

            'user_name',

            'first_name',

            'reports_to_id',

          'mycustomfield',

         ),

         'link_name_to_fields_array' => array(),

        );

    $get_entries_result = call("get_entries", $get_entries_parameters, $url);

all value are return except my customfield how i get this.