Router works for POST requests.

lib/Config/Initializer.php

@@ -1,6 +1,7 @@
 <?php
 namespace MailPoet\Config;
 use MailPoet\Models;
+use MailPoet\Router;
 
 if(!defined('ABSPATH')) exit;
 
@@ -18,6 +19,7 @@ class Initializer {
     $this->setupRenderer();
     $this->setupLocalizer();
     $this->setupMenu();
+    $this->setupRouter();
   }
 
   function setupDB() {
@@ -54,4 +56,9 @@ class Initializer {
     );
     $menu->init();
   }
+
+  function setupRouter() {
+    $router = new Router\Router();
+    $router->init();
+  }
 }

lib/Router/Router.php

@@ -8,29 +8,36 @@ class Router {
   }
 
   function init() {
+    add_action(
+      'admin_head',
+      array($this, 'setToken')
+    );
     add_action(
       'wp_ajax_mailpoet',
       array($this, 'setup')
     );
-    $this->setToken();
   }
 
   function setup() {
     $this->securityCheck();
-    $endpoint =  ucfirst($_POST['endpoint']);
-    $action = $_POST['action'];
+    $class = ucfirst($_POST['endpoint']);
+    $endpoint =  __NAMESPACE__ . "\\" . $class;
+    $method = $_POST['method'];
     $args = $_POST['args'];
-    $route = new $endpoint();
-    $route->$action($args);
+    $endpoint = new $endpoint();
+    $endpoint->$method(json_encode($args));
   }
 
   function setToken() {
     $token = wp_create_nonce('mailpoet_token');
-    wp_localize_script($token);
+    $global = '<script type="text/javascript">';
+    $global .= 'var mailpoet_token = "' . $token . '";';
+    $global .= "</script>/n";
+    echo $global;
   }
 
   function securityCheck() {
     if (!current_user_can('manage_options')) {die();}
-    if (!wp_verify_nonce($_POST['token'])) {die();}
+    if (!wp_verify_nonce($_POST['token'], 'mailpoet_token')) {die();}
   }
 }

lib/Router/Settings.php

@@ -13,6 +13,6 @@ class Settings {
       'last_name' => 'Mailer',
       'email' => 'john@mailpoet.com'
     );
-    echo json_encode($data);
+    wp_send_json($params);
   }
 }

views/settings.html

@@ -32,34 +32,24 @@
     </p>
   </form>
 
-  <script type="text/javascript">
-  jQuery(function($) {
-
-    function loadSettings() {
-    var data = {
-      'endpoint': 'settings',
-      'action': 'get',
-      'args': ''
-    };
-
-    $.post(ajaxurl, data, function(response) {
-      alert('Server response from the AJAX URL ' + response);
-    });
+<script type="text/javascript">
+jQuery(document).ready(function($) {
+  $.ajax({
+    url: ajaxurl,
+    type: 'post',
+    data: {
+      action: 'mailpoet',
+      token: mailpoet_token,
+      endpoint: 'settings',
+      method: 'get',
+      args: {
+        first_name: 'John'
+      }
+    },
+    success : function(response) {
+      console.log(response);
     }
-
-    function saveSettings() {
-      console.log('save settings...');
-
-      return false;
-    }
-
-    // save settings on form submission
-    $(document).on('submit', '#mailpoet_settings', saveSettings);
-
-    // on dom loaded
-    $(function() {
-      loadSettings();
-    });
   });
-  </script>
+});
+</script>
 <% endblock %>