试试这个：

function prefix_get_users(){
  $args=array(
    \'blog_id\' => $GLOBALS[\'blog_id\']
  );
  $all_users=get_users($args);
  $arr=array();
  foreach ($all_users as $val) {
    $arr[]=$val->data->user_nicename;
  }
  die(json_encode( $arr ));
}