wp-includes/post.php:8285Checks the given subset of the post hierarchy for hierarchy loops.
$post_parentint$post_idintintfunction 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 ( ! $post_id ) { return $post_parent; } // Can't be its own parent. if ( $post_parent === $post_id ) { return 0; } // Now look for larger loops. $loop = wp_find_hierarchy_loop( 'wp_get_post_parent_id', $post_id, $post_parent ); if ( ! $loop ) { 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;}Introduced in 3.1.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/post.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.