Can’t get_users info by using json_encode

Try this code

function get_users(){
    $all_users = get_users();
    $arr=array();

    foreach ($all_users as $val) {
       $arr[]=array( 'value'=> $val->data->user_nicename, 'label'=> $val->data->display_name, 'icon' => get_avatar_url($val->ID));
    }
    wp_send_json($arr);
}