<?php
defined('ABSPATH') || exit;
/**
* Outputs the Mailchimp Site Tracking Pixel SDK script
* and identifies subscribers after successful form submissions.
*
* @since 4.13.0
* @access private
* @ignore
*/
class MC4WP_Tracking_Pixel
{
/**
* @var string The foreign_id / site_id used to identify the connected site in Mailchimp.
*/
private $site_id;
/**
* @var string Email address of a subscriber to identify, set during form processing.
*/
private $identify_email = '';
/**
* @param string $site_id The connected site ID stored in the plugin options.
*/
public function __construct(string $site_id)
{
$this->site_id = $site_id;
}
/**
* Register hooks for outputting the tracking pixel.
*
* @return void
*/
public function add_hooks(): void
{
add_action('wp_head', [$this, 'output_tracking_script']);
add_action('mc4wp_form_subscribed', [$this, 'capture_subscriber_email'], 10, 2);
add_action('wp_footer', [$this, 'output_identify_script'], 99);
}
/**
* Output the Mailchimp Site Tracking Pixel SDK script tag.
*
* @return void
*/
public function output_tracking_script(): void
{
if (empty($this->site_id)) {
return;
}
$opts = mc4wp_get_options();
if (empty($opts['tracking_pixel_script_url'])) {
return;
}
wp_enqueue_script('mc4wp-mailchimp-site-tracking-pixel', $opts['tracking_pixel_script_url'], [], MC4WP_VERSION, [
'strategy' => 'defer',
]);
}
/**
* Capture the subscriber email after a successful form subscription.
*
* Fires during the mc4wp_form_subscribed action hook.
*
* @since 4.13.0
*
* @param MC4WP_Form $form The submitted form instance.
* @param string $email The subscriber's email address.
* @return void
*/
public function capture_subscriber_email($form, string $email): void
{
$this->identify_email = $email;
}
/**
* Output inline script to identify the subscriber via the Mailchimp pixel SDK.
*
* Only outputs when a subscriber email was captured during this request.
*
* @since 4.13.0
*
* @return void
*/
public function output_identify_script(): void
{
if (empty($this->identify_email) || empty($this->site_id)) {
return;
}
echo '<script>';
echo 'if(window.$mcSite&&window.$mcSite.pixel&&window.$mcSite.pixel.api){';
echo 'window.$mcSite.pixel.api.identify({type:"EMAIL",value:"' . esc_js($this->identify_email) . '"});';
echo '}';
echo '</script>' . "\n";
}
/**
* Auto-fetch an existing Mailchimp Connected Site that matches the current domain,
* or create a new one if none is found.
*
* @since 4.13.0
*
* @param string $api_key API key to use. Defaults to the configured one, pass this explicitly when
* the key is about to change since the API service holds the stored key.
*
* @return array{site_id: string, script_url: string}|false Array with site data on success, false on failure.
*/
public static function fetch_or_create_connected_site(string $api_key = '')
{
try {
/** @var MC4WP_API_V3 $api */
$api = $api_key === '' ? mc4wp_get_service('api') : new MC4WP_API_V3($api_key);
$foreign_id = self::get_foreign_id();
$domain = self::get_site_domain();
$matched_site = null;
// First, look the site up by its foreign_id directly. The e-commerce add-on registers a
// connected site using the store ID, so this normally hits on the first try.
try {
$site = $api->get_connected_site($foreign_id);
if (isset($site->domain) && self::normalize_domain($site->domain) === $domain) {
$matched_site = $site;
} else {
// The ID belongs to a different domain, so using its script would track the wrong
// site. Make the ID unique to this domain in case we end up registering below.
$foreign_id .= '-' . substr(md5($domain), 0, 8);
}
} catch (MC4WP_API_Resource_Not_Found_Exception $e) {
// No connected site registered under this ID yet.
}
// Otherwise, look for an existing site registered under the same domain.
if (null === $matched_site) {
foreach ($api->get_connected_sites() as $site) {
$site_domain = isset($site->domain) ? self::normalize_domain($site->domain) : '';
if ('' !== $site_domain && $site_domain === $domain) {
$matched_site = $site;
break;
}
}
}
// Still nothing, so register a new connected site. Mailchimp rejects a second site for a
// domain that is already connected, which is why both lookups above run first.
if (null === $matched_site) {
$matched_site = $api->add_connected_site([
'foreign_id' => $foreign_id,
'domain' => $domain,
]);
}
return [
'site_id' => sanitize_text_field($matched_site->foreign_id ?? $matched_site->id ?? ''),
'script_url' => esc_url_raw($matched_site->site_script->url ?? ''),
];
} catch (Exception $e) {
// Cast the exception to string so Mailchimp's own error detail ends up in the log,
// instead of just the HTTP status message.
mc4wp_get_service('log')->error(sprintf('Tracking Pixel: error fetching/creating connected site. %s', (string) $e));
return false;
}
}
/**
* Returns the domain to register this site under in Mailchimp.
*
* @return string
*/
public static function get_site_domain(): string
{
$home_url = get_home_url();
$domain = self::normalize_domain($home_url);
$path = trim((string) wp_parse_url($home_url, PHP_URL_PATH), '/');
// Mailchimp strips the subdirectory part off a domain, which would make every site in a
// subdirectory network resolve to the same domain. Turn each path segment into a hostname
// label instead, deepest first, so /shop becomes shop.example.com like the e-commerce add-on
// registers it and a nested /network/shop becomes shop.network.example.com.
if ($path !== '' && is_multisite()) {
$labels = array_map([ __CLASS__, 'to_hostname_label' ], array_reverse(explode('/', $path)));
$labels = array_filter($labels);
if (! empty($labels)) {
$domain = implode('.', $labels) . '.' . $domain;
}
}
return $domain;
}
/**
* Turns a single URL path segment into something usable as a hostname label.
*
* @param string $segment
* @return string
*/
private static function to_hostname_label(string $segment): string
{
$label = strtolower(rawurldecode($segment));
$label = (string) preg_replace('/[^a-z0-9-]+/', '-', $label);
$label = trim((string) preg_replace('/-+/', '-', $label), '-');
return substr($label, 0, 63);
}
/**
* Reduces a URL or domain to the bare hostname Mailchimp stores it as, so that two spellings of
* the same site compare equal. Strips the protocol, port, path and the www. prefix.
*
* @param string $url
* @return string
*/
private static function normalize_domain(string $url): string
{
$url = trim($url);
// Add a scheme-relative prefix so the host is parsed as such for bare domains too.
if (strpos($url, '//') === false) {
$url = '//' . ltrim($url, '/');
}
$host = strtolower((string) wp_parse_url($url, PHP_URL_HOST));
if (strpos($host, 'www.') === 0) {
$host = substr($host, 4);
}
return $host;
}
/**
* Returns a foreign_id to use when registering a new connected site.
* Reuses the e-commerce store ID when available so Mailchimp can link them.
*
* @return string
*/
private static function get_foreign_id(): string
{
// Read through the add-on's own getter when available, because it fills in a default store ID
// at runtime that is not always written back to the option.
if (function_exists('mc4wp_ecommerce_get_settings')) {
$ecommerce_settings = mc4wp_ecommerce_get_settings();
} else {
$ecommerce_settings = get_option('mc4wp_ecommerce', []);
}
if (is_array($ecommerce_settings) && ! empty($ecommerce_settings['store_id'])) {
return (string) $ecommerce_settings['store_id'];
}
// sanitize_title() percent-encodes names without any latin characters, so strip anything
// that is not safe to use as an identifier.
$slug = substr((string) preg_replace('/[^a-z0-9-]/', '', sanitize_title(get_bloginfo('name'))), 0, 32);
if ($slug === '') {
$slug = 'site';
}
return 'mc4wp-' . $slug . '-' . get_current_blog_id();
}
}