How to Rewrite Guest Author Name with Custom Fields in WordPress

Have you ever had a guest post on your blog? How do you go about giving the author full credit? We have seen many sites where they add an author profile box either above the post or below the post. But even with the guest author box, the author name field would still show the site author. Some bloggers create entire new author profiles for their guest authors in order to display the right name. We think that it is pointless to create extra user profiles if you know that this guest author will only post once.