How to use filter on comment submission/insert

Question

I am working on a small project for my family to share info, recipes etc. And I added a "@" mention feature. Now that the mention feature works I need to notify the user they were mentioned.

I thought that the WP comments already kind of do this and since my family would be getting comment notifications via email I decided to insert a comment when a mention happens into the DB. It uses comment type "mention" and set the comment_post_ID to 0 and add a bit of comment meta data to store the user who was mentioned and the one that did the mentioning. It works pretty well.

I can send an email using wp_mail no problem but since the "mentions" are "comments" I wanted to use anything WP already had to offer. I found two methods that may help: wp_notify_postauthor and comment_post.

Using comment_post worked but it only sent out for normal comments.

I tried filtering and hooking into wp_notify_postauthor with no luck. Here's what I have for filtering the wp_notify_postauthor:

add_filter('wp_notify_postauthor', 'smile_wp_send_member_notification', 10, 2);

function smile_wp_send_member_notification( $comment_id, $comment_type ){

    ob_start();

    //get comment info
    $comment = get_comment( $comment_id );
    $from_user = $comment->user_id;
    $post = get_post( $comment->comment_post_ID );
    $author = get_userdata( $post->post_author );

    //set email subject
    $email_subject = $comment->comment_type.' notification title';

    include('email_header.php');
    ?>

    <p>
        <?php echo $comment->comment_type; ?> <?php echo $post->post_type; ?> Notification Message in here.<br />
        <?php echo $comment->comment_content; ?>
    </p>

    <?php 

    include('email_footer.php');

    $message = ob_get_contents();

    //clear buffer
    ob_end_clean();

    //ob_start();
    //wp_mail( $author->user_email, $email_subject, $message );
    //ob_end_clean();

    return $message;

}//end smile_wp_send_member_notification

I though wp_notify_postauthor was pluggable but maybe not. If there is another way to perform this or get the email notification to send please let me know.

Answer 1

There is no wp_notify_postauthor filter, a pluggable function is one you override with your own function:

if( ! function_exists('wp_notify_postauthor') ) {
    function wp_notify_postauthor( $comment_id, $comment_type = '' ) {
        // your own wp_notify_postauthor code
    }
}

I suggest looking at the function in source to see what it does.

Answer 2

Turns out the notification email is only sent if the comment_post_ID is not 0. I altered my notification comments code to set the comment_post_ID and now it all works!