Add back to post link on blank comment post error page

Question

When you visit any wordpress post and click on the "Post Comment" button it just post that blank data to the server and while doing the check at php level it shows this annoying error message to users:

we all have seen it. but what I was wondering is if there is a way to add a "Back to XYZ Article" link in there. Where XYZ Artcile is the post page he way visiting while he accidentally clicked that post comment button.

It happens to many people many times.

Looking forward to your ideas.

Answer 1

I think 'pre_comment_on_post' is a better hook to use, although you'll have to reproduce some logic from "wp-comments-post.php" to use it, eg:

add_action( 'pre_comment_on_post', function ( $comment_post_ID ) {
    $go_back = sprintf( __( '<br><a href="javascript:history.go(-1)">Back to "%s" Article</a>' ), get_the_title( $comment_post_ID ) );
    // Part-copied from "wp-comments-post.php", with $go_back tagged onto error strings.
    $comment_author       = ( isset($_POST['author']) )  ? trim(strip_tags($_POST['author'])) : null;
    $comment_author_email = ( isset($_POST['email']) )   ? trim($_POST['email']) : null;
    $comment_content      = ( isset($_POST['comment']) ) ? trim($_POST['comment']) : null;
    $user = wp_get_current_user();
    if ( get_option('require_name_email') && !$user->exists() ) {
        if ( 6 > strlen( $comment_author_email ) || '' == $comment_author ) {
            wp_die( __( '<strong>ERROR</strong>: please fill the required fields (name, email).' ) . $go_back, 200 );
        } elseif ( ! is_email( $comment_author_email ) ) {
            wp_die( __( '<strong>ERROR</strong>: please enter a valid email address.' ) . $go_back, 200 );
        }
    }
    if ( '' == $comment_content ) {
        wp_die( __( '<strong>ERROR</strong>: please type a comment.' ) . $go_back, 200 );
    }
} );

Answer 2

I don't see any hook there, but you could use the gettext filter hook. Adding the following function to your theme's functions.php should do the trick. Replace text-domain with your theme's text domain.

if ( ! function_exists( 'my_gettext' ) ) {
    function my_gettext( $translated_text, $untranslated_text, $domain ) {
        global $pagenow;

        if ( $pagenow === 'wp-comments-post.php' ) {
            switch ( $untranslated_text ) {
                case '<strong>ERROR</strong>: please fill the required fields (name, email).' :
                    $translated_text = __( '<strong>ERROR</strong>: please fill the required fields (name, email).<br /><a href="javascript:javascript:history.go(-1)">Back to XYZ Article</a>', 'text-domain' );
                    break;
            }
        }
        return $translated_text;
    }
}
add_filter( 'gettext', 'my_gettext', 20, 3 );

The function looks for the case in wp-comments-post.php and replaces it with the $translated_text.

The downside is that we would normally not include HTML in internationalization functions, yet splitting it doesn't work. So, the following would throw an error:

$translated_text = '<strong>' . __( 'ERROR', 'text-domain' ) . '</strong>:' . __( 'please fill the required fields (name, email).', 'text-domain' ) . '<br /><a href="javascript:javascript:history.go(-1)">' . __( 'Back to XYZ Article', 'text-domain' ) . '</a>';

---

UPDATE following Pieter's comment

Just for the record, with sprinf it is indeed not necessary to include HTML in internationalization functions...

if ( ! function_exists( 'my_gettext' ) ) {
    function my_gettext( $translated_text, $untranslated_text, $domain ) {
        global $pagenow;
        if ( $pagenow === 'wp-comments-post.php' ) {
            switch ( $untranslated_text ) {
                case '<strong>ERROR</strong>: please fill the required fields (name, email).' :
                    $translated_text = sprintf( __( '%1$s: please fill the required fields (name, email).%2$s', 'text-domain' ), '<strong>' . __( 'ERROR', 'text-domain' ) . '</strong>', '<br /><a href="javascript:javascript:history.go(-1)">' . __( 'Back to XYZ Article', 'text-domain' ) . '</a>' );
                    break;
            }
        }
        return $translated_text;
    }
}
add_filter( 'gettext', 'my_gettext', 20, 3 );