Valid HTML and XHTML documents should include a DOCTYPE declaration. Besides being difficult to remember, these can also affect how certain elements in your document should be rendered (for instance, CDATA escaping in <script> and <style> elements.

The Doctype helper allows you to specify one of the following types:

You can also specify a custom doctype as long as it is well-formed.

The Doctype helper is a concrete implementation of the Placeholder helper.

Basic Usage

You may specify the doctype at any time. However, helpers that depend on the doctype for their output will recognize it only after you have set it, so the easiest approach is to specify it in your bootstrap:

use Zend\View\Helper\Doctype;

$doctypeHelper = new Doctype();

And then print it out on top of your layout script:

<?php echo $this->doctype() ?>

Within an application based off the skeleton application, you can specify the doctype via configuration:

// module/Application/config/module.config.php:
return [
    /* ... */
    'view_manager' => [
        'doctype' => 'html5',
        /* ... */

Retrieving the Doctype

If you need to know the doctype, you can do so by calling getDoctype() on the helper, which is returned by invoking the helper from the view.

$doctype = $this->doctype()->getDoctype();

Typically, you'll want to know if the doctype is XHTML or not; for this, the isXhtml() method will suffice:

if ($this->doctype()->isXhtml()) {
    // do something differently

You can also check if the doctype represents an HTML5 document.

if ($this->doctype()->isHtml5()) {
    // do something differently

Choosing a Doctype to Use with the Open Graph Protocol

To implement the Open Graph Protocol, you may specify the XHTML1_RDFA doctype. This doctype allows a developer to use the Resource Description Framework within an XHTML document.

use Zend\View\Helper\Doctype;

$doctypeHelper = new Doctype();

The RDFa doctype allows XHTML to validate when the 'property' meta tag attribute is used per the Open Graph Protocol spec. Example within a view script:

<?= $this->doctype('XHTML1_RDFA'); ?>
<html xmlns=""
   <meta property="og:type" content="musician" />

In the previous example, we set the property to og:type. The og references the Open Graph namespace we specified in the html tag. The content identifies the page as being about a musician. See the Open Graph Protocol documentation for supported properties. The HeadMeta helper may be used to programmatically set these Open Graph Protocol meta tags.

Here is how you check if the doctype is set to XHTML1_RDFA:

<?= $this->doctype() ?>
<html xmlns=""
    <?php if ($view->doctype()->isRdfa()): ?>
    <?php endif; ?>

Zend MVC View Manager

If you're running a ZendMvc application, you should specify doctype via the ViewManager service.