In your view scripts, often it is necessary to perform certain complex functions over and over: e.g., formatting a date, generating form elements, or displaying action links. You can use helper, or plugin, classes to perform these behaviors for you.
A helper is simply a class that implements Zend\View\Helper\HelperInterface and it simply defines two methods, setView(), which accepts a Zend\View\Renderer\RendererInterface instance/implementation, and getView(), used to retrieve that instance. Zend\View\Renderer\PhpRenderer composes a plugin manager, allowing you to retrieve helpers, and also provides some method overloading capabilities that allow proxying method calls to helpers.
As an example, let’s say we have a helper class named MyModule\View\Helper\LowerCase, which we register in our plugin manager with the name “lowercase”. We can retrieve it in one of the following ways:
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// $view is a PhpRenderer instance // Via the plugin manager: $pluginManager = $view->getHelperPluginManager(); $helper = $pluginManager->get('lowercase'); // Retrieve the helper instance, via the method "plugin", // which proxies to the plugin manager: $helper = $view->plugin('lowercase'); // If the helper does not define __invoke(), the following also retrieves it: $helper = $view->lowercase(); // If the helper DOES define __invoke, you can call the helper // as if it is a method: $filtered = $view->lowercase('some value');
The last two examples demonstrate how the PhpRenderer uses method overloading to retrieve and/or invoke helpers directly, offering a convenience API for end users.
A large number of helpers are provided in the standard distribution of Zend Framework. You can also register helpers by adding them to the plugin manager.
Zend Framework comes with an initial set of helper classes. In particular, there are helpers for creating route-based URLs and HTML lists, as well as declaring variables. Additionally, there are a rich set of helpers for providing values for, and rendering, the various HTML <head> tags, such as HeadTitle, HeadLink, and HeadScript. The currently shipped helpers include:
- HTML Object Plugins
View helpers related to Internationalization are documented in the I18n View Helpers chapter.
View helpers related to form are documented in the Form View Helpers chapter.
View helpers related to navigation are documented in the Navigation View Helpers chapter.
View helpers related to paginator are documented in the Paginator Usage chapter.
For documentation on writing custom view helpers see the Advanced usage chapter.