NOTE: Instructions are wrong, correction inside

The instructions under “installation” are wrong.

Add the following class to the entire form (or individual text/textarea fields), not “gplaceholder”:

gf-add-placeholder

However

If you want your select boxes to have the placeholder, you do have to use:

gplaceholder

on the select field.

https://ww.wp.xz.cn/plugins/gravity-forms-placeholders/