How to validate field when create post

Question

I have a custom CPT and I need that my user fill all the required fields.
How can I check if the field is set and show a message error if is not set?

I have a custom hook to the save_post action that check if is my CPT, there is any action for show error box and prevent create post?

Answer 1

You can check post data in $_POST array on save_post_{custom_post_type_name} action hook.

And if data is not appropriate or according to server side validation and redirect page with custom error args using wp_redirect and , you can grab the errors and display admin notices using admin_notice.