main bootstrapping callback can be anonymous function

mailchimp-for-wp.php

@@ -32,21 +32,13 @@
 // Prevent direct file access
 defined('ABSPATH') or exit;
 
-
-
-
-/** @ignore */
-function _mc4wp_load_plugin()
-{
+// bootstrap main plugin
+add_action('plugins_loaded', function () {
     global $mc4wp;
 
     // don't run if Mailchimp for WP Pro 2.x is activated
-    if (defined('MC4WP_VERSION')) {
-        return;
-    }
-
     // don't run if PHP version is lower than 7.4.0
-    if (PHP_VERSION_ID < 70400) {
+    if (defined('MC4WP_VERSION') || PHP_VERSION_ID < 70400) {
         return;
     }
 
@@ -101,10 +93,7 @@ function _mc4wp_load_plugin()
 
     // bootstrap integrations
     require __DIR__ . '/integrations/bootstrap.php';
-}
-
-// bootstrap main plugin
-add_action('plugins_loaded', '_mc4wp_load_plugin', 8);
+}, 8);
 
 // schedule the action hook to refresh the stored Mailchimp lists on a daily basis
 register_activation_hook(__FILE__, function () {