Cannot add user fields

Your plugin fails here, most notably fails to add user fields (status 500 Internal server error) even before I have tried to use it for real. I found the reason. My wp-config.php is not located where you assume it to be.

A plugin cannot know where to find wp-config.php. It may be either in the root folder or the folder above it. Including wp-config.php is always wrong. To load WordPress from a plugin file, and axjax handler, like php/add_field.php you may use wp-load.php, even if such a way to implement ajax is also bad.

Please substitute
` require_once(“../../../../wp-config.php”);
with
require_once("../../../../wp-load.php");

But to do it properly read this
http://solislab.com/blog/5-tips-for-using-ajax-in-wordpress/

https://ww.wp.xz.cn/plugins/wpsc-support-tickets/