Bootstrap官网用法:http://getbootstrap.com/javascript/#dropdowns

原文如下：

data-toggle="dropdown" still required

Regardless of whether you call your dropdown via JavaScript or instead use the data-api, data-toggle="dropdown" is always required to be present on the dropdown's trigger element.

即不能去掉data-toggle="dropdown"

<?php
echo '不知道 不知道';
?>