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Zend_Layout
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Zend_Layout Quick Start

There are two primary use cases for Zend_Layout: with the Zend Framework MVC, and without.

Layout scripts

In both cases, however, you'll need to create a layout script. Layout scripts simply utilize Zend_View (or whatever view implementation you are using). Layout variables are registered with a Zend_Layout placeholder, and may be accessed via the placeholder helper or by fetching them as object properties of the layout object via the layout helper.

As an example: 

<!DOCTYPE html
    PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>My Site</title>
</head>
<body>
<?php
    // fetch 'content' key using layout helper:
    echo $this->layout()->content;

    // fetch 'foo' key using placeholder helper:
    echo $this->placeholder('Zend_Layout')->foo;

    // fetch layout object and retrieve various keys from it:
    $layout = $this->layout();
    echo $layout->bar;
    echo $layout->baz;
?>
</body>
</html>

Because Zend_Layout utilizes Zend_View for rendering, you can also use any view helpers registered, and also have access to any previously assigned view variables. Particularly useful are the various placeholder helpers, as they allow you to retrieve content for areas such as the <head> section, navigation, etc.: 

<!DOCTYPE html
    PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <?php echo $this->headTitle() ?>
    <?php echo $this->headScript() ?>
    <?php echo $this->headStyle() ?>
</head>
<body>
    <?php echo $this->render('header.phtml') ?>

    <div id="nav"><?php echo $this->placeholder('nav') ?></div>

    <div id="content"><?php echo $this->layout()->content ?></div>

    <?php echo $this->render('footer.phtml') ?>
</body>
</html>

Using Zend_Layout with the Zend Framework MVC

Zend_Controller offers a rich set of functionality for extension via its front controller plugins and action controller helpers. Zend_View also has helpers. Zend_Layout takes advantage of these various extension points when used with the MVC components.

Zend_Layout::startMvc() creates an instance of Zend_Layout with any optional configuration you provide it. It then registers a front controller plugin that renders the layout with any application content once the dispatch loop is done, and registers an action helper to allow access to the layout object from your action controllers. Additionally, you may at any time grab the layout instance from within a view script using the Layout view helper.

First, let's look at how to initialize Zend_Layout for use with the MVC: 

// In your bootstrap:
Zend_Layout::startMvc();

startMvc() can take an optional array of options or Zend_Config object to customize the instance; these options are detailed in this section.

In an action controller, you may then access the layout instance as an action helper: 

class FooController extends Zend_Controller_Action
{
    public function barAction()
    {
        // disable layouts for this action:
        $this->_helper->layout->disableLayout();
    }

    public function bazAction()
    {
        // use different layout script with this action:
        $this->_helper->layout->setLayout('foobaz');
    };
}

In your view scripts, you can then access the layout object via the Layout view helper. This view helper is slightly different than others in that it takes no arguments, and returns an object instead of a string value. This allows you to immediately call methods on the layout object: 

<?php $this->layout()->setLayout('foo'); // set alternate layout ?>

At any time, you can fetch the Zend_Layout instance registered with the MVC via the getMvcInstance() static method: 

// Returns null if startMvc() has not first been called
$layout = Zend_Layout::getMvcInstance();

Finally, Zend_Layout's front controller plugin has one important feature in addition to rendering the layout: it retrieves all named segments from the response object and assigns them as layout variables, assigning the 'default' segment to the variable 'content'. This allows you to access your application content and render it in your view scripts.

As an example, let's say your code first hits FooController::indexAction(), which renders some content to the default response segment, and then forwards to NavController::menuAction(), which renders content to the 'nav' response segment. Finally, you forward to CommentController::fetchAction() and fetch some comments, but render those to the default response segment as well (which appends content to that segment). Your view script could then render each separately: 

<body>
    <!-- renders /nav/menu -->
    <div id="nav"><?php echo $this->layout()->nav ?></div>

    <!-- renders /foo/index + /comment/fetch -->
    <div id="content"><?php echo $this->layout()->content ?></div>
</body>

This feature is particularly useful when used in conjunction with the ActionStack action helper and plugin, which you can use to setup a stack of actions through which to loop, and thus create widgetized pages.

Using Zend_Layout as a Standalone Component

As a standalone component, Zend_Layout does not offer nearly as many features or as much convenience as when used with the MVC. However, it still has two chief benefits:

  • Scoping of layout variables.

  • Isolation of layout view script from other view scripts.

When used as a standalone component, simply instantiate the layout object, use the various accessors to set state, set variables as object properties, and render the layout: 

$layout = new Zend_Layout();

// Set a layout script path:
$layout->setLayoutPath('/path/to/layouts');

// set some variables:
$layout->content = $content;
$layout->nav     = $nav;

// choose a different layout script:
$layout->setLayout('foo');

// render final layout
echo $layout->render();

Sample Layout

Sometimes a picture is worth a thousand words. The following is a sample layout script showing how it might all come together.

The actual order of elements may vary, depending on the CSS you've setup; for instance, if you're using absolute positioning, you may be able to have the navigation displayed later in the document, but still show up at the top; the same could be said for the sidebar or header. The actual mechanics of pulling the content remain the same, however.

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