Get name and email of current unregistered user, who has recently submitted name and email in comment form?

Question

From within a WordPress plugin, is there any way to get the name and email of the current user, when s/he is not logged in, but has recently submitted a comment, and specified name and email in the comment reply form?

Or is the name & email only available during the HTTP request in which [the comment posted by the user] is being processed?

(When the the user is not logged in, the WP_User returned by wp_get_current_user() contains no info on the user's email or name, I've noticed when debugging.)

(Background: I'm writing a comment rating plugin, and I'd like to highlight the user's ratings, even if s/he isn't a registered user. As mentioned in the comments below, perhaps some cookie will be needed in any case. I'm still interested in knowing the answer to this question however, perhaps I could reuse some existing functionality or something)

Answer 1

An unregistered user's name and email are available in cookies, once s/he has left a comment. The cookies are named like:

comment_author_3e6aea64ec43ed661a5dee3433f1e8bc
comment_author_email_3e6aea64ec43ed661a5dee3433f1e8bc

You can retrieve them like so:

sanitize_comment_cookies();
wp_get_current_commenter(); // returns comment_author,
                            //   comment_author_email, comment_author_url

They're created here in comment.php:

/**
 * Sets the cookies used to store an unauthenticated commentator's identity. Typically used
 * to recall previous comments by this commentator that are still held in moderation.
 *
 * @param object $comment Comment object.
 * @param object $user Comment author's object.
 *
 * @since 3.4.0
 */
function wp_set_comment_cookies($comment, $user) {
    if ( $user->exists() )
        return;

    $comment_cookie_lifetime = apply_filters('comment_cookie_lifetime', 30000000);
    setcookie('comment_author_' . COOKIEHASH, $comment->comment_author, ...);
    setcookie('comment_author_email_' . COOKIEHASH, $comment->comment_author_email, ...);
    setcookie('comment_author_url_' . COOKIEHASH, ...);
}

(I found out by stepping through wp-comments-post.php with a debugger.)

((As mentioned in the comments below the original question above, couldn't this sometimes be a privacy issue, if someone posts a comment in a public library — then the one who uses the computer afterwards might find those comments that are "waiting for authentication", and know who wrote them, hmm))