Topic Tag: Forms with post relationships

Problem: I have a one-to-many post relationship set up in Types. When I create a child post in wp-admin, I would like to automatically set the child post title based on the parent post's title, using save_post.

Solution: Use the post relationships API toolset_get_related_post to retrieve the parent post ID during the save_post hook when saving a child post. Then use WordPress API wp_update_post to set the child post title automatically.

$parent_id = toolset_get_related_post( $post_id, 'relationship-slug' );

Relevant Documentation:
https://toolset.com/documentation/customizing-sites-using-php/post-relationships-api/#toolset_get_related_post
https://developer.wordpress.org/reference/functions/wp_update_post/
https://developer.wordpress.org/reference/hooks/save_post/