diff --git a/controllers/Dispatcher.php b/controllers/Dispatcher.php
index 91bc7175..966f7da6 100644
--- a/controllers/Dispatcher.php
+++ b/controllers/Dispatcher.php
@@ -3,7 +3,7 @@
  * Zookeeper Online
  *
  * @author Jim Mason <jmason@ibinx.com>
- * @copyright Copyright (C) 1997-2019 Jim Mason <jmason@ibinx.com>
+ * @copyright Copyright (C) 1997-2021 Jim Mason <jmason@ibinx.com>
  * @link https://zookeeper.ibinx.com/
  * @license GPL-3.0
  *
@@ -34,6 +34,7 @@
 
 require_once __DIR__."/../vendor/autoload.php";
 
+use ZK\Engine\Config;
 use ZK\Engine\Engine;
 
 class Dispatcher {
@@ -42,32 +43,27 @@ class Dispatcher {
 
     public function __construct() {
         // UI configuration file
-        include __DIR__.'/../config/ui_config.php';
-        if(isset($menu) && is_array($menu)) {
-            $this->menu = $menu;
-            $customMenu = Engine::param('custom_menu');
-            if($customMenu)
-                $this->menu = array_merge($this->menu, $customMenu);
-        }
+        $this->menu = new Config('ui_config', 'menu');
+        $customMenu = Engine::param('custom_menu');
+        if($customMenu)
+            $this->menu->merge($customMenu);
 
         // Controllers
-        if(isset($controllers)) {
-            $this->controllers = $controllers;
-            $customControllers = Engine::param('custom_controllers');
-            if($customControllers)
-                $this->controllers = array_merge($this->controllers, $customControllers);
-        }
+        $this->controllers = new Config('ui_config', 'controllers');
+        $customControllers = Engine::param('custom_controllers');
+        if($customControllers)
+            $this->controllers->merge($customControllers);
     }
 
     /**
      * return menu entry that matches the specified action
      */
     public function match($action) {
-        foreach($this->menu as $entry) {
+        return $this->menu->iterate(function($entry) use($action) {
             if($entry[1] == $action || substr($entry[1], -1) == '%' &&
                     substr($entry[1], 0, -1) == substr($action, 0, strlen($entry[1])-1))
                 return $entry;
-        }
+        });
     }
 
     /**
@@ -79,7 +75,7 @@ public function dispatch($action, $subaction, $session) {
         // If no action was selected or if action is unauthorized,
         // default to the first one
         if(!$entry || !$session->isAuth($entry[0]))
-            $entry = $this->menu[0];
+            $entry = $this->menu->default();
 
         $handler = new $entry[3]();
         if($handler instanceof CommandTarget)
@@ -98,8 +94,8 @@ public function isActionAuth($action, $session) {
      * compose the menu for the specified session
      */
     public function composeMenu($action, $session) {
-        $result = array();
-        foreach ($this->menu as $entry) {
+        $result = [];
+        $this->menu->iterate(function($entry) use(&$result, $action, $session) {
             if($entry[2] && $session->isAuth($entry[0])) {
                 $baseAction = substr($entry[1], -1) == '%'?
                             substr($entry[1], 0, -1):$entry[1];
@@ -111,7 +107,7 @@ public function composeMenu($action, $session) {
                               'label' => $entry[2],
                               'selected' => $selected ];
             }
-        }
+        });
         return $result;
     }
 
@@ -119,13 +115,11 @@ public function composeMenu($action, $session) {
      * dispatch request to the specified controller
      */
     public function processRequest($controller="") {
-        if(isset($this->controllers)) {
-            if(empty($controller) ||
-                    !array_key_exists($controller, $this->controllers))
-                $controller = array_keys($this->controllers)[0];
-            $impl = new $this->controllers[$controller]();
-            if($impl instanceof IController)
-                $impl->processRequest($this);
-        }
+        $implClass = empty($controller) ||
+                        !($p = $this->controllers->getParam($controller)) ?
+            $this->controllers->default():$p;
+        $impl = new $implClass();
+        if($impl instanceof IController)
+            $impl->processRequest($this);
     }
 }
diff --git a/engine/Config.php b/engine/Config.php
index e509960e..698d3625 100644
--- a/engine/Config.php
+++ b/engine/Config.php
@@ -3,7 +3,7 @@
  * Zookeeper Online
  *
  * @author Jim Mason <jmason@ibinx.com>
- * @copyright Copyright (C) 1997-2018 Jim Mason <jmason@ibinx.com>
+ * @copyright Copyright (C) 1997-2021 Jim Mason <jmason@ibinx.com>
  * @link https://zookeeper.ibinx.com/
  * @license GPL-3.0
  *
@@ -30,34 +30,73 @@
 class Config {
     private $config;
 
-    public function init($file) {
-        // populate the config property from the given file
-        include $file;
-        if(isset($config) && is_array($config))
-            $this->config = $config;
+    /**
+     * ctor
+     *
+     * @param file base filename of configuration file (without extension)
+     * @param variable variable name in config file (default 'config')
+     */
+    public function __construct($file, $variable = 'config') {
+        // populate the configuration from the given file and variable
+        include __DIR__."/../config/${file}.php";
+        if(isset($$variable) && is_array($$variable))
+            $this->config = $$variable;
+        else
+            throw new \Exception("Error parsing configuration: file=${file}.php, variable=${variable}");
     }
 
     /**
-     * get a configuration value from the configuration file
+     * merge an array of entries into this configuration
      *
-     * @param key name of param
-     * @param default value if param is not set (optional)
-     * @return value or null if not set and no default specified
+     * @param config array to merge
      */
-    public function getParam($key, $default = null) {
-        return isset($this->config) &&
-                   array_key_exists($key, $this->config)?
-                   $this->config[$key]:$default;
+    public function merge($config) {
+        $this->config = array_merge($this->config, $config);
+    }
+
+    /**
+     * iterate over the entries in the configuration
+     *
+     * calls user-supplied callback for each entry.
+     * iteration ceases upon first non-null return value from the callback
+     *
+     * @param fn callback with signature 'function($entry)'
+     * @return first value returned by a callback, if any
+     */
+    public function iterate($fn) {
+        foreach($this->config as $entry)
+            if(($x = $fn($entry)) !== null)
+                return $x;
     }
 
     /**
-     * set a configurate value in the in-memory configuration data
+     * return the default (first) configuration entry
+     *
+     * @return default entry
+     */
+    public function default() {
+        return $this->config[array_keys($this->config)[0]];
+    }
+
+    /**
+     * determine whether the specified configuration param exists
+     *
+     * @param key name of param to test
+     * @return true if exists, false otherwise
+     */
+    public function hasParam($key) {
+        return array_key_exists($key, $this->config);
+    }
+
+    /**
+     * get a configuration value from the configuration file
      *
      * @param key name of param
-     * @param value value to set
+     * @param default value if param is not set (optional)
+     * @return value or null if not set and no default specified
      */
-    public function setParam($key, $value) {
-        if(isset($this->config))
-            $this->config[$key] = $value;
+    public function getParam($key, $default = null) {
+        return array_key_exists($key, $this->config)?
+                   $this->config[$key]:$default;
     }
 }
diff --git a/engine/Engine.php b/engine/Engine.php
index 234cbec3..f86aabfd 100644
--- a/engine/Engine.php
+++ b/engine/Engine.php
@@ -54,12 +54,10 @@ public static function init() {
         self::customAutoloader();
 
         // application configuration file
-        self::$config = new Config();
-        self::$config->init(__DIR__.'/../config/config.php');
+        self::$config = new Config('config');
 
         // engine configuration file
-        self::$apis = new Config();
-        self::$apis->init(__DIR__.'/../config/engine_config.php');
+        self::$apis = new Config('engine_config');
 
         self::$session = new Session();
     }