UPDATE: The plugin from the tutorial is now available on the WordPress plugin repository – After Comment Prompts

A few months ago, I wanted to create a way to prompt my readers to follow me on Twitter after they leave a comment on one of my posts. There are already a few solutions available to do this sort of thing (like the Yoast Comment Hacks plugin) but not one that did things the way I wanted, which was redirecting a user to the comment’s permalink, like normal, and displaying a modal window with my message, as in the image below.

I also wanted to make it easy to customize, so I added a setting to display any type of content and customizer options to adjust the design of the modal and overlay.

I put this all into a plugin that is available on GitHub. Instead of walking you through all of the code, I’m going to walk you through the main purpose: doing something after a user submits a comment on a post.

The Code

The most important part of this functionality is the comment_post_redirect filter. This runs after a comment has been submitted and it modifies the redirect URL (to where to user is sent after submitting). The function we’re tying to this filter accepts two parameters: $location and $comment.

/**
 *	Redirect to a custom URL after a comment is submitted
 *	Added query arg used for displaying prompt
 *
 *	@param string $location Redirect URL
 *	@param object $comment Comment object
 *	@return string $location New redirect URL
 */
function comment_post_redirect( $location, $comment ) {

	$location = add_query_arg( array(
		'comment_added' => $comment->comment_ID
	), $location );

	return $location;
}

Specifically, this code is appending a query argument to the default URL. The default URL is the post’s permalink with the ID of the comment’s container. This means that, by default, the user is redirected to view the comment he or she just submitted. If you’ve ever commented on a WordPress blog, you’re likely familiar with this process.

We are adding a custom query argument so that we can check to see if it’s set and show our modal prompt accordingly.

/**
 *	Add the content for the prompt modal
 */
function add_prompt_content() {

	// Bail if the functionality is not enabled
	if ( ! after_comment_prompts_is_enabled() ) {
		return;
	}

	// Bail if comment_added query arg is not set or is something other than a number
	if ( ! isset( $_GET['comment_added'] ) || ! is_numeric( $_GET['comment_added'] ) ) {
		return;
	}

	// Bail if the modal is disable for logged-in users
	if ( after_comment_prompts_is_hidden_for_logged_in() && is_user_logged_in() ) {
		return;
	}

	// Comment object
	$comment = get_comment( $_GET['comment_added'] );

	if ( ! $comment ) {
		return;
	}

	// Commenter's first name
	$author_names = explode( ' ', $comment->comment_author );
	$author_fname = $author_names[0];

	// Message setting value
	$message = after_comment_prompts_get_settings()['message'];

	// Replace merge tags
	$message = str_replace( '{commenter_name}', $author_fname, $message );

	// Final output
	$output = after_comment_prompts_get_modal( $message );

	echo apply_filters( 'after_comment_prompts_modal_output_comments', $output, $comment, $message );
}

Next, we’re checking to see if the comment_added query argument is set. If it’s not, then we’re not going to run anything further. Otherwise, we’ll continue.

Assuming the comment_added argument is set, we use the value of that argument to retrieve the comment object. From the comment object, we get the author’s name and the default message we set in the plugin’s settings. Then, we replace the {commenter_name} merge tag with the author’s first name and output the message using the modal script and markup created elsewhere in the code.

Summary

Feel free to take a look at the rest of the code if you want to know more about how it works. If you’re not into code, just download and install the plugin and configure you’re settings.