通过助手模式，可以把一些经常使用的功能模块做封装，从而在可以在需要的地方灵活使用，主要是在action使用。
Zend Framework中有两种助手，动作助手(Zend_Controller_Action_Helper)和试图助手(Zend_View_Helper)。
动作助手可以向任何Zend_Controller_Action的衍生动作控制器中，即时的加入功能(runtime and/or on-demand functionality)，以使得增加公共的动作控制器功能时，尽量减少衍生动作控制器类的必要。
动作助手在需要调用时加载，可以在请求的时候(bootstrap)或者动作控制器创建的时候(init())实例化。
涉及到的相关文件
在/library/Zend/Controller/Action/中
│ Exception.php
│ HelperBroker.php
│ Interface.php
│
├─Helper
│ │ Abstract.php
│ │ ActionStack.php
│ │ AjaxContext.php
│ │ AutoCompleteDojo.php
│ │ AutoCompleteScriptaculous.php
│ │ Cache.php
│ │ ContextSwitch.php
│ │ FlashMessenger.php
│ │ Json.php
│ │ Redirector.php
│ │ Url.php
│ │ ViewRenderer.php
│ │
│ └─AutoComplete
│ Abstract.php
│
└─HelperBroker
PriorityStack.php
常见的动作助手有：
FlashMessenger 用来处理Flash Messenger会话；
Json 用来解码和发送 JSON 响应；
Url 用于创建Urls；
Redirector 提供另一种实现方式，帮助程序重定向到内部或者外部页面；
ViewRenderer 自动的完成在控制器内建立视图对象并渲染视图的过程；
AutoComplete 自动响应 AJAX 的自动完成；
ContextSwitch 和 AjaxContext 为你的动作提供替代响应格式；
Cache 实现cache的相关操作；
ActionStack 用于操作动作堆栈。
动手的几种实例化使用方式
1.通过Zend_Controller_Action的 $_helper成员的getHelper()方法。直接调用getHelper()，传入助手的名称即可。
$redirector = $this->_helper->getHelper('Redirector');
//$redirector->getName();
$redirector->gotoSimple('index2');
2.直接通过访问的_helper助手的属性对应的助手对象。
$redirector = $this->_helper->Redirector;
Zend_Controller_Action_HelperBroker
中文名称译作"助手经纪人",顾名思义，是动作助手的中间人。
在动作的实例化使用的方式的第二种方式就是通过Zend_Controller_Action_HelperBroker的魔术方法__get()来实现的。
助手经纪人用于注册助手对象和助手路径以及获取助手等等功能。
Zend_Controller_Action_HelperBroker的实现以及常用方法列表
<?php /** * @see Zend_Controller_Action_HelperBroker_PriorityStack */require_once 'Zend/Controller/Action/HelperBroker/PriorityStack.php';/** * @see Zend_Loader */require_once 'Zend/Loader.php';/** * @category Zend * @package Zend_Controller * @subpackage Zend_Controller_Action * @copyright Copyright (c) 2005-2011 Zend Technologies USA Inc. (http://www.zend.com) * @license http://framework.zend.com/license/new-bsd New BSD License */class Zend_Controller_Action_HelperBroker{ /** * $_actionController - ActionController reference * * @var Zend_Controller_Action */ protected $_actionController; /** * @var Zend_Loader_PluginLoader_Interface */ protected static $_pluginLoader; /** * $_helpers - Helper array * * @var Zend_Controller_Action_HelperBroker_PriorityStack */ protected static $_stack = null; /** * Set PluginLoader for use with broker * * @param Zend_Loader_PluginLoader_Interface $loader * @return void */ public static function setPluginLoader($loader) { if ((null !== $loader) && (!$loader instanceof Zend_Loader_PluginLoader_Interface)) { require_once 'Zend/Controller/Action/Exception.php'; throw new Zend_Controller_Action_Exception('Invalid plugin loader provided to HelperBroker'); } self::$_pluginLoader = $loader; } /** * Retrieve PluginLoader * * @return Zend_Loader_PluginLoader */ public static function getPluginLoader() { if (null === self::$_pluginLoader) { require_once 'Zend/Loader/PluginLoader.php'; self::$_pluginLoader = new Zend_Loader_PluginLoader(array( 'Zend_Controller_Action_Helper' => 'Zend/Controller/Action/Helper/', )); } return self::$_pluginLoader; } /** * addPrefix() - Add repository of helpers by prefix * * @param string $prefix */ static public function addPrefix($prefix) { $prefix = rtrim($prefix, '_'); $path = str_replace('_', DIRECTORY_SEPARATOR, $prefix); self::getPluginLoader()->addPrefixPath($prefix, $path); } /** * addPath() - Add path to repositories where Action_Helpers could be found. * * @param string $path * @param string $prefix Optional; defaults to 'Zend_Controller_Action_Helper' * @return void */ static public function addPath($path, $prefix = 'Zend_Controller_Action_Helper') { self::getPluginLoader()->addPrefixPath($prefix, $path); } /** * addHelper() - Add helper objects * * @param Zend_Controller_Action_Helper_Abstract $helper * @return void */ static public function addHelper(Zend_Controller_Action_Helper_Abstract $helper) { self::getStack()->push($helper); return; } /** * resetHelpers() * * @return void */ static public function resetHelpers() { self::$_stack = null; return; } /** * Retrieve or initialize a helper statically * * Retrieves a helper object statically, loading on-demand if the helper * does not already exist in the stack. Always returns a helper, unless * the helper class cannot be found. * * @param string $name * @return Zend_Controller_Action_Helper_Abstract */ public static function getStaticHelper($name) { $name = self::_normalizeHelperName($name); $stack = self::getStack(); if (!isset($stack->{$name})) { self::_loadHelper($name); } return $stack->{$name}; } /** * getExistingHelper() - get helper by name * * Static method to retrieve helper object. Only retrieves helpers already * initialized with the broker (either via addHelper() or on-demand loading * via getHelper()). * * Throws an exception if the referenced helper does not exist in the * stack; use {@link hasHelper()} to check if the helper is registered * prior to retrieving it. * * @param string $name * @return Zend_Controller_Action_Helper_Abstract * @throws Zend_Controller_Action_Exception */ public static function getExistingHelper($name) { $name = self::_normalizeHelperName($name); $stack = self::getStack(); if (!isset($stack->{$name})) { require_once 'Zend/Controller/Action/Exception.php'; throw new Zend_Controller_Action_Exception('Action helper "' . $name . '" has not been registered with the helper broker'); } return $stack->{$name}; } /** * Return all registered helpers as helper => object pairs * * @return array */ public static function getExistingHelpers() { return self::getStack()->getHelpersByName(); } /** * Is a particular helper loaded in the broker? * * @param string $name * @return boolean */ public static function hasHelper($name) { $name = self::_normalizeHelperName($name); return isset(self::getStack()->{$name}); } /** * Remove a particular helper from the broker * * @param string $name * @return boolean */ public static function removeHelper($name) { $name = self::_normalizeHelperName($name); $stack = self::getStack(); if (isset($stack->{$name})) { unset($stack->{$name}); } return false; } /** * Lazy load the priority stack and return it * * @return Zend_Controller_Action_HelperBroker_PriorityStack */ public static function getStack() { if (self::$_stack == null) { self::$_stack = new Zend_Controller_Action_HelperBroker_PriorityStack(); } return self::$_stack; } /** * Constructor * * @param Zend_Controller_Action $actionController * @return void */ public function __construct(Zend_Controller_Action $actionController) { $this->_actionController = $actionController; foreach (self::getStack() as $helper) { $helper->setActionController($actionController); $helper->init(); } } /** * notifyPreDispatch() - called by action controller dispatch method * * @return void */ public function notifyPreDispatch() { foreach (self::getStack() as $helper) { $helper->preDispatch(); } } /** * notifyPostDispatch() - called by action controller dispatch method * * @return void */ public function notifyPostDispatch() { foreach (self::getStack() as $helper) { $helper->postDispatch(); } } /** * getHelper() - get helper by name * * @param string $name * @return Zend_Controller_Action_Helper_Abstract */ public function getHelper($name) { $name = self::_normalizeHelperName($name); $stack = self::getStack(); if (!isset($stack->{$name})) { self::_loadHelper($name); } $helper = $stack->{$name}; $initialize = false; if (null === ($actionController = $helper->getActionController())) { $initialize = true; } elseif ($actionController !== $this->_actionController) { $initialize = true; } if ($initialize) { $helper->setActionController($this->_actionController) ->init(); } return $helper; } /** * Method overloading * * @param string $method * @param array $args * @return mixed * @throws Zend_Controller_Action_Exception if helper does not have a direct() method */ public function __call($method, $args) { $helper = $this->getHelper($method); if (!method_exists($helper, 'direct')) { require_once 'Zend/Controller/Action/Exception.php'; throw new Zend_Controller_Action_Exception('Helper "' . $method . '" does not support overloading via direct()'); } return call_user_func_array(array($helper, 'direct'), $args); } /** * Retrieve helper by name as object property * * @param string $name * @return Zend_Controller_Action_Helper_Abstract */ public function __get($name) { return $this->getHelper($name); } /** * Normalize helper name for lookups * * @param string $name * @return string */ protected static function _normalizeHelperName($name) { if (strpos($name, '_') !== false) { $name = str_replace(' ', '', ucwords(str_replace('_', ' ', $name))); } return ucfirst($name); } /** * Load a helper * * @param string $name * @return void */ protected static function _loadHelper($name) { try { $class = self::getPluginLoader()->load($name); } catch (Zend_Loader_PluginLoader_Exception $e) { require_once 'Zend/Controller/Action/Exception.php'; throw new Zend_Controller_Action_Exception('Action Helper by name ' . $name . ' not found', 0, $e); } $helper = new $class(); if (!$helper instanceof Zend_Controller_Action_Helper_Abstract) { require_once 'Zend/Controller/Action/Exception.php'; throw new Zend_Controller_Action_Exception('Helper name ' . $name . ' -> class ' . $class . ' is not of type Zend_Controller_Action_Helper_Abstract'); } self::getStack()->push($helper); }}助手经纪人的常见用法：
一、注册一个助手
1.Zend_Controller_Action_HelperBroker::addHelper($helper);
2.通过addPrefix()方法带有一个类前缀参数，用来加入自定义助手类的路径。
要求前缀遵循Zend Framework的类命名惯例。
// Add helpers prefixed with My_Action_Helpers in My/Action/Helpers/
Zend_Controller_Action_HelperBroker::addPrefix('My_Action_Helpers');
3.使用addPath()方法第一个参数为一个目录，第二个为类前缀(默认为'Zend_Controller_Action_Helper')。
用来将自己的类前缀映射到指定的目录。
// Add helpers prefixed with Helper in Plugins/Helpers/
Zend_Controller_Action_HelperBroker::addPath('./Plugins/Helpers',
'Helper');
二、判读助手是否存在
使用hasHelper($name)方法来判定助手经纪人中是否存在某助手，$name是助手的短名称（去掉前缀的）：
// Check if 'redirector' helper is registered with the broker:
if (Zend_Controller_Action_HelperBroker::hasHelper('redirector')) {
echo 'Redirector helper registered';
}
从助手经纪人中获取助手有两个静态方法：getExistingHelper() 和 getStaticHelper() 。getExistingHelper()将获取助手仅当它以前调用过或者显性地通过助手经纪人注册过，否则就抛出一个异常。getStaticHelper() 的做法和getExistingHelper()一样，但如果还没有注册助手堆栈，它将尝试初始化助手，为获取你要配置的的助手，getStaticHelper()是一个好的选择。
两个方法都带一个参数，$name，它是助手的短名称（去掉前缀）。
// Check if 'redirector' helper is registered with the broker, and fetch:
if (Zend_Controller_Action_HelperBroker::hasHelper('redirector')) {
$redirector =
Zend_Controller_Action_HelperBroker::getExistingHelper('redirector');
}
// Or, simply retrieve it, not worrying about whether or not it was
// previously registered:
$redirector =
Zend_Controller_Action_HelperBroker::getStaticHelper('redirector');
}
三、removeHelper($name)删除助手经纪人中的某个助手，$name是助手的短名称。
// Conditionally remove the 'redirector' helper from the broker:
if (Zend_Controller_Action_HelperBroker::hasHelper('redirector')) {
Zend_Controller_Action_HelperBroker::removeHelper('redirector')
}
下面介绍如何自定义助手。