post_parent in custom post type

Question

I've two custom post types, type1 and type2

My current workflow of creating contents, from the user perspective

• a user created posts of type1, i.e. post1, post2, post3 on a particular day
• our system automatic create a post of type2 is at the end of the day, i.e. `post
• the post_parent of post1, post2, post3 are set to post4

So, there are two cases:

• How to auto reset the post_parent of post1, post2, post3 when post4 is deleted? (I want to retain post1, post2, post3)
• How to auto delete post1, post2, post3 when post4 is deleted? (I want cleanup)

Answer 1

Hook in when a post is deleted, check for the post type, then manipulate post_parent of potential child posts (or delete the posts):

function wp_dev_174635_update_posts( $parent_id ) {

    $parent = get_post( $parent_id );
    if ( $parent->post_type !== 'type2' ) {
        return;
    }

    $posts = get_posts( array(
        'post_type'   => 'type1',
        'post_parent' => $parent_id,
    ) );
    foreach ( $posts as $post ) {
        // EITHER: Reset post parent entry
        wp_update_post( array(
            'ID'          => $post->ID,
            'post_parent' => 0,
        ) );

        // OR: Delete post
        // wp_delete_post( $post->ID );
    }
}

add_action( 'delete_post', 'wp_dev_174635_update_posts' );