View Helper - HeadMeta

Introduction

The HTML <meta> element is used to provide meta information about your HTML document – typically keywords, document character set, caching pragmas, etc. Meta tags may be either of the ‘http-equiv’ or ‘name’ types, must contain a ‘content’ attribute, and can also have either of the ‘lang’ or ‘scheme’ modifier attributes.

The HeadMeta helper supports the following methods for setting and adding meta tags:

• appendName($keyValue, $content, $conditionalName)
• offsetSetName($index, $keyValue, $content, $conditionalName)
• prependName($keyValue, $content, $conditionalName)
• setName($keyValue, $content, $modifiers)
• appendHttpEquiv($keyValue, $content, $conditionalHttpEquiv)
• offsetSetHttpEquiv($index, $keyValue, $content, $conditionalHttpEquiv)
• prependHttpEquiv($keyValue, $content, $conditionalHttpEquiv)
• setHttpEquiv($keyValue, $content, $modifiers)
• setCharset($charset)

The following methods are also supported with XHTML1_RDFA doctype set with the Doctype helper:

• appendProperty($property, $content, $modifiers)
• offsetSetProperty($index, $property, $content, $modifiers)
• prependProperty($property, $content, $modifiers)
• setProperty($property, $content, $modifiers)

The $keyValue item is used to define a value for the ‘name’ or ‘http-equiv’ key; $content is the value for the ‘content’ key, and $modifiers is an optional associative array that can contain keys for ‘lang’ and/or ‘scheme’.

You may also set meta tags using the headMeta() helper method, which has the following signature: headMeta($content, $keyValue, $keyType = 'name', $modifiers = array(), $placement = 'APPEND'). $keyValue is the content for the key specified in $keyType, which should be either ‘name’ or ‘http-equiv’. $keyType may also be specified as ‘property’ if the doctype has been set to XHTML1_RDFA. $placement can be ‘SET’ (overwrites all previously stored values), ‘APPEND’ (added to end of stack), or ‘PREPEND’ (added to top of stack).

HeadMeta overrides each of append(), offsetSet(), prepend(), and set() to enforce usage of the special methods as listed above. Internally, it stores each item as a stdClass token, which it later serializes using the itemToString() method. This allows you to perform checks on the items in the stack, and optionally modify these items by simply modifying the object returned.

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

Basic Usage

You may specify a new meta tag at any time. Typically, you will specify client-side caching rules or SEO keywords.

For instance, if you wish to specify SEO keywords, you’d be creating a meta name tag with the name ‘keywords’ and the content the keywords you wish to associate with your page:

// setting meta keywords
$this->headMeta()->appendName('keywords', 'framework, PHP, productivity');

If you wished to set some client-side caching rules, you’d set http-equiv tags with the rules you wish to enforce:

// disabling client-side cache
$this->headMeta()->appendHttpEquiv('expires',
                                   'Wed, 26 Feb 1997 08:21:57 GMT')
                 ->appendHttpEquiv('pragma', 'no-cache')
                 ->appendHttpEquiv('Cache-Control', 'no-cache');

Another popular use for meta tags is setting the content type, character set, and language:

// setting content type and character set
$this->headMeta()->appendHttpEquiv('Content-Type',
                                   'text/html; charset=UTF-8')
                 ->appendHttpEquiv('Content-Language', 'en-US');

If you are serving an HTML5 document, you should provide the character set like this:

// setting character set in HTML5
$this->headMeta()->setCharset('UTF-8'); // Will look like <meta charset="UTF-8">

As a final example, an easy way to display a transitional message before a redirect is using a “meta refresh”:

// setting a meta refresh for 3 seconds to a new url:
$this->headMeta()->appendHttpEquiv('Refresh',
                                   '3;URL=http://www.some.org/some.html');

When you’re ready to place your meta tags in the layout, simply echo the helper:

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

Usage with XHTML1_RDFA doctype

Enabling the RDFa doctype with the Doctype helper enables the use of the ‘property’ attribute (in addition to the standard ‘name’ and ‘http-equiv’) with HeadMeta. This is commonly used with the Facebook Open Graph Protocol.

For instance, you may specify an open graph page title and type as follows:

$this->doctype(Zend\View\Helper\Doctype::XHTML_RDFA);
$this->headMeta()->setProperty('og:title', 'my article title');
$this->headMeta()->setProperty('og:type', 'article');
echo $this->headMeta();

// output is:
//   <meta property="og:title" content="my article title" />
//   <meta property="og:type" content="article" />