Why is wp_is_post_revision always false?

Question

I am trying to save a revision of a custom post type. This is what I have to check if the post has a parent:

function save_revision( $post ) {

    if ( $post['submitted'] == true ) {
       $parent_id = wp_is_post_revision( $post['post_id'] );
       ...
    }
} add_action('init', 'save_revision');

The problem is that I always get false for $parent_id even though I know there is a parent post for that post_id.

Any help is appreciated, I have been trying to get this to work forever.

Answer 1

I know this is an old thread, but for future reference - the term "revision" in Wordpress is a little confusing. It's not the updated, or revised, post... but the older version. The most updated version is the "parent."

So, if you're calling the function wp_is_revision_post() on the current version of the post, it will always return false (and wp_get_post_parent_id() will return NULL) since the current post is not considered a "revision." You will need to call it on an actual revision, (which would have a different ID from the current version of the post).

Answer 2

It is simple: If $post is not a revision, wp_is_post_revision() returns false; just reading the name of the function give you the reason. wp_is_post_revision() returns the parent post ID only if the given post is a revision (a revision has always a parent post). It seems that you want to get the parent post ID of $post, not checking if $post is a revision.

To get the parent post ID of another post use wp_get_post_parent_id():

function save_revision( $post ) {

    if ( $post['submitted'] == true ) {
       $parent_id = wp_get_post_parent_id( $post['post_id'] );
       ...
    }
}
add_action('init', 'save_revision');