wp_check_post_hierarchy_for_loops

Source code

function wp_check_post_hierarchy_for_loops( $post_parent, $post_ID ) {

	// Nothing fancy here - bail

	if ( !$post_parent )

		return 0;



	// New post can't cause a loop

	if ( empty( $post_ID ) )

		return $post_parent;



	// Can't be its own parent

	if ( $post_parent == $post_ID )

		return 0;



	// Now look for larger loops



	if ( !$loop = wp_find_hierarchy_loop( 'wp_get_post_parent_id', $post_ID, $post_parent ) )

		return $post_parent; // No loop



	// Setting $post_parent to the given value causes a loop

	if ( isset( $loop[$post_ID] ) )

		return 0;



	// There's a loop, but it doesn't contain $post_ID.  Break the loop.

	foreach ( array_keys( $loop ) as $loop_member )

		wp_update_post( array( 'ID' => $loop_member, 'post_parent' => 0 ) );



	return $post_parent;

}