您可以使用 $。trim（） 如下：

You can fix it on the client side using $.trim() like this:

if($.trim(data) == 'success') {

线来自服务器端，可能是您的PHP中某个错误的新行，检查<？之前或之后

Or, a better approach would be removing the new-line coming from the server-side, probably an erroneous new-line in your PHP somewhere, check before or after the <? ?> block, this is most often where they crop up.

或者，在输出内容后退出，如下所示：

Or, just exit after outputting your content, like this:

if($update) {
  echo 'success';
  exit();
}