# Zend_Layout Advanced Usage

Zend_Layout has a number of use cases for the advanced developer who wishes to adapt it for different view implementations, file system layouts, and more.

The major points of extension are:

- Custom view objects. Zend_Layout allows you to utilize any class that implements Zend_View_Interface.

- Custom front controller plugins. Zend_Layout ships with a standard front controller plugin that automates rendering of layouts prior to returning the response. You can substitute your own plugin.

- Custom action helpers. Zend_Layout ships with a standard action helper that should be suitable for most needs as it is a dumb proxy to the layout object itself.

- Custom layout script path resolution. Zend_Layout allows you to use your own inflector for layout script path resolution, or simply to modify the attached inflector to specify your own inflection rules.

## Custom View Objects

Zend_Layout allows you to use any class implementing Zend_View_Interface or extending Zend_View_Abstract for rendering your layout script. Simply pass in your custom view object as a parameter to the constructor/startMvc(), or set it using the setView() accessor:

    $view = new My_Custom_View();
    $layout->setView($view);

Not all Zend_View implementations are equal

While Zend_Layout allows you to use any class implementing Zend_View_Interface, you may run into issues if they can not utilize the various Zend_View helpers, particularly the layout and placeholder helpers. This is because Zend_Layout makes variables set in the object available via itself and placeholders.

If you need to use a custom Zend_View implementation that does not support these helpers, you will need to find a way to get the layout variables to the view. This can be done by either extending the Zend_Layout object and altering the render() method to pass variables to the view, or creating your own plugin class that passes them prior to rendering the layout.

Alternately, if your view implementation supports any sort of plugin capability, you can access the variables via the 'Zend_Layout' placeholder, using the placeholder helper:

    $placeholders = new Zend_View_Helper_Placeholder();
    $layoutVars   = $placeholders->placeholder('Zend_Layout')->getArrayCopy();

## Custom Front Controller Plugins

When used with the MVC components, Zend_Layout registers a front controller plugin that renders the layout as the last action prior to exiting the dispatch loop. In most cases, the default plugin will be suitable, but should you desire to write your own, you can specify the name of the plugin class to load by passing the pluginClass option to the startMvc() method.

Any plugin class you write for this purpose will need to extend Zend_Controller_Plugin_Abstract, and should accept a layout object instance as an argument to the constructor. Otherwise, the details of your implementation are up to you.

The default plugin class used is Zend_Layout_Controller_Plugin_Layout.

## Custom Action Helpers

When used with the MVC components, Zend_Layout registers an action controller helper with the helper broker. The default helper, Zend_Layout_Controller_Action_Helper_Layout, acts as a dumb proxy to the layout object instance itself, and should be suitable for most use cases.

Should you feel the need to write custom functionality, simply write an action helper class extending Zend_Controller_Action_Helper_Abstract and pass the class name as the helperClass option to the startMvc() method. Details of the implementation are up to you.

## Custom Layout Script Path Resolution: Using the Inflector

Zend_Layout uses Zend_Filter_Inflector to establish a filter chain for translating a layout name to a layout script path. By default, it uses the rules 'Word_CamelCaseToDash' followed by 'StringToLower', and the suffix 'phtml' to transform the name to a path. As some examples:

- 'foo' will be transformed to 'foo.phtml'.

- 'FooBarBaz' will be transformed to 'foo-bar-baz.phtml'.

You have three options for modifying inflection: modify the inflection target and/or view suffix via Zend_Layout accessors, modify the inflector rules and target of the inflector associated with the Zend_Layout instance, or create your own inflector instance and pass it to Zend_Layout::setInflector().

Using Zend_Layout accessors to modify the inflector

The default Zend_Layout inflector uses static references for the target and view script suffix, and has accessors for setting these values.

    // Set the inflector target:
    $layout->setInflectorTarget('layouts/:script.:suffix');

    // Set the layout view script suffix:
    $layout->setViewSuffix('php');

Direct modification of Zend_Layout inflector

Inflectors have a target and one or more rules. The default target used with Zend_Layout is ':script.:suffix'; ':script' is passed the registered layout name, while ':suffix' is a static rule of the inflector.

Let's say you want the layout script to end in the suffix 'html', and that you want to separate MixedCase and camelCased words with underscores instead of dashes, and not lowercase the name. Additionally, you want it to look in a 'layouts' subdirectory for the script.

    $layout->getInflector()->setTarget('layouts/:script.:suffix')
                           ->setStaticRule('suffix', 'html')
                           ->setFilterRule(array('Word_CamelCaseToUnderscore'));

Custom inflectors

In most cases, modifying the existing inflector will be enough. However, you may have an inflector you wish to use in several places, with different objects of different types. Zend_Layout supports this.

    $inflector = new Zend_Filter_Inflector('layouts/:script.:suffix');
    $inflector->addRules(array(
        ':script' => array('Word_CamelCaseToUnderscore'),
        'suffix'  => 'html'
    ));
    $layout->setInflector($inflector);

Inflection can be disabled

Inflection can be disabled and enabled using accessors on the Zend_Layout object. This can be useful if you want to specify an absolute path for a layout view script, or know that the mechanism you will be using for specifying the layout script does not need inflection. Simply use the enableInflector() and disableInflector() methods.