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In cms-admin.php page i have this error:
Warning: Undefined array key "publish_at" in D:\wamp64\www\....\cmsadmin.php on line 1047
Warning: Undefined array key "unpublish_at" in D:\wamp64\www\....\cmsadmin.php on line 1049
In cmsadmin.php at the two positions I have:
1047 - $publish_at_value = $data['publish_at'];
1049 - $unpublish_at_value = $data['unpublish_at'];

To solve the problem, it is necessary to permanently modify the page script:
1047 - $publish_at = $_POST['publish_at'] ?? null;
1049 - $unpublish_at = $_POST['unpublish_at'] ?? null;

, which is not possible for the WWB user because with each republishing of the site it returns to the initial values. I know that I can use fcgid_module in wampserver, but it is preferable without it, considering the new version of wwb(21). Thank you.

The code you have added makes is not correct in this context. The error is unrelated to php 8.5. It means that the fields do not exists.
You will need to update the structure of the CMS database to make sure these two field exists.

Ok ...And how can i solve this:
Warning: Undefined array key "publish_at" in D:\wamp64\www\workpage\cmsadmin.php on line 1047
Warning: Undefined array key "unpublish_at" in D:\wamp64\www\workpage\cmsadmin.php on line 1049 ? Because the script is automatically generated...Two tables must be added manually to the cms db (publish_at and unpublish_at)

You will need to add the fields
publish_at
unpublish_at
to the CMS database.

The SQL statement to create the table is documented in the help and on the website.
https://www.wysiwygwebbuilder.com/cms_database.html

If you are able to log in via your host using phpMyAdmin, you should be able to add the required columns to your database without using SQL