get_post_author() by Post ID in WordPress

WordPress doesn’t have a native get_post_author() function you can call to get the user ID for the author of a post. This function can be used for that purpose:

/**
 * @param int $post_id Post ID.
 *
 * @return int Post author ID.
 */
function get_post_author( $post_id ) {
  return get_post_field( 'post_author', $post_id );
}

You could of course just call get_post_field( 'post_author', $post_id ) directly, but wrapping it in the get_post_author() function results in slightly better semantics and more readable code, since the function name communicates its purpose.