An HTML5 parser and serializer.

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2.1.2 2015-06-07 08:43 UTC


The need for an HTML5 parser in PHP is clear. This project initially began with the seemingly abandoned html5lib project original source. But after some initial refactoring work, we began a new parser.

  • An HTML5 serializer
  • Support for PHP namespaces
  • Composer support
  • Event-based (SAX-like) parser
  • DOM tree builder
  • Interoperability with QueryPath [in progress]
  • Runs on PHP 5.3.0 or newer and HHVM 3.2 or newer

Build Status Latest Stable Version Code Coverage Scrutinizer Code Quality


Install HTML5-PHP using composer.

To install, add masterminds/html5 to your composer.json file:

  "require" : {
    "masterminds/html5": "2.*"

(You may substitute 2.* for a more specific release tag, of course.)

From there, use the composer install or composer update commands to install.

Basic Usage

HTML5-PHP has a high-level API and a low-level API.

Here is how you use the high-level HTML5 library API:

// Assuming you installed from Composer:
require "vendor/autoload.php";
use Masterminds\HTML5;

// An example HTML document:
$html = <<< 'HERE'
  <body id='foo'>
    <h1>Hello World</h1>
    <p>This is a test of the HTML5 parser.</p>

// Parse the document. $dom is a DOMDocument.
$html5 = new HTML5();
$dom = $html5->loadHTML($html);

// Render it as HTML5:
print $html5->saveHTML($dom);

// Or save it to a file:
$html5->save($dom, 'out.html');


The $dom created by the parser is a full DOMDocument object. And the save() and saveHTML() methods will take any DOMDocument.


It is possible to pass in an array of configuration options when loading an HTML5 document.

// An associative array of options
$options = array(
  'option_name' => 'option_value',

// Provide the options to the constructor
$html5 = new HTML5($options);

$dom = $html5->loadHTML($html);

The following options are supported:

  • encode_entities (boolean): Indicates that the serializer should aggressively encode characters as entities. Without this, it only encodes the bare minimum.
  • disable_html_ns (boolean): Prevents the parser from automatically assigning the HTML5 namespace to the DOM document. This is for non-namespace aware DOM tools.
  • target_document (\DOMDocument): A DOM document that will be used as the destination for the parsed nodes.
  • implicit_namespaces (array): An assoc array of namespaces that should be used by the parser. Name is tag prefix, value is NS URI.

The Low-Level API

This library provides the following low-level APIs that you can use to create more customized HTML5 tools:

  • An InputStream abstraction that can work with different kinds of input source (not just files and strings).
  • A SAX-like event-based parser that you can hook into for special kinds of parsing.
  • A flexible error-reporting mechanism that can be tuned to document syntax checking.
  • A DOM implementation that uses PHP's built-in DOM library.

The unit tests exercise each piece of the API, and every public function is well-documented.

Parser Design

The parser is designed as follows:

  • The InputStream portion handles direct I/O.
  • The Scanner handles scanning on behalf of the parser.
  • The Tokenizer requests data off of the scanner, parses it, clasifies it, and sends it to an EventHandler. It is a recursive descent parser.
  • The EventHandler receives notifications and data for each specific semantic event that occurs during tokenization.
  • The DOMBuilder is an EventHandler that listens for tokenizing events and builds a document tree (DOMDocument) based on the events.

Serializer Design

The serializer takes a data structure (the DOMDocument) and transforms it into a character representation -- an HTML5 document.

The serializer is broken into three parts:

  • The OutputRules contain the rules to turn DOM elements into strings. The rules are an implementation of the interface RulesInterface allowing for different rule sets to be used.
  • The Traverser, which is a special-purpose tree walker. It visits each node node in the tree and uses the OutputRules to transform the node into a string.
  • HTML5 manages the Traverser and stores the resultant data in the correct place.

The serializer (save(), saveHTML()) follows the section 8.9 of the HTML 5.0 spec. So tags are serialized according to these rules:

  • A tag with children: <foo>CHILDREN</foo>
  • A tag that cannot have content: <foo> (no closing tag)
  • A tag that could have content, but doesn't: <foo></foo>

Known Issues (Or, Things We Designed Against the Spec)

Please check the issue queue for a full list, but the following are issues known issues that are not presently on the roadmap:

  • Namespaces: HTML5 only supports a selected list of namespaces and they do not operate in the same way as XML namespaces. A : has no special meaning. By default the parser does not support XML style namespaces via :; to enable the XML namespaces see the XML Namespaces section
  • Scripts: This parser does not contain a JavaScript or a CSS interpreter. While one may be supplied, not all features will be supported.
  • Rentrance: The current parser is not re-entrant. (Thus you can't pause the parser to modify the HTML string mid-parse.)
  • Validation: The current tree builder is not a validating parser. While it will correct some HTML, it does not check that the HTML conforms to the standard. (Should you wish, you can build a validating parser by extending DOMTree or building your own EventHandler implementation.)
    • There is limited support for insertion modes.
    • Some autocorrection is done automatically.
    • Per the spec, many legacy tags are admitted and correctly handled, even though they are technically not part of HTML5.
  • Attribute names and values: Due to the implementation details of the PHP implementation of DOM, attribute names that do not follow the XML 1.0 standard are not inserted into the DOM. (Effectively, they are ignored.) If you've got a clever fix for this, jump in!
  • Processor Instructions: The HTML5 spec does not allow processor instructions. We do. Since this is a server-side library, we think this is useful. And that means, dear reader, that in some cases you can parse the HTML from a mixed PHP/HTML document. This, however, is an incidental feature, not a core feature.
  • HTML manifests: Unsupported.
  • PLAINTEXT: Unsupported.
  • Adoption Agency Algorithm: Not yet implemented. (

XML Namespaces

To use XML style namespaces you have to configure well the main HTML5 instance.

use Masterminds\HTML5;
$html = new HTML5(array(
    "xmlNamespaces" => true

$dom = $html->loadHTML('<t:tag xmlns:t=""/>');

$dom->documentElement->namespaceURI; //

You can also add some default prefixes that will not require the namespace declaration, but it's elements will be namespaced.

use Masterminds\HTML5;
$html = new HTML5(array(

$dom = $html->loadHTML('<t:tag/>');

$dom->documentElement->namespaceURI; //

Thanks to...

The dedicated (and patient) contributors of patches small and large, who have already made this library better.See the CREDITS file for a list of contributors.

We owe a huge debt of gratitude to the original authors of html5lib.

While not much of the orignal parser remains, we learned a lot from reading the html5lib library. And some pieces remain here. In particular, much of the UTF-8 and Unicode handling is derived from the html5lib project.


This software is released under the MIT license. The original html5lib library was also released under the MIT license.


Certain files contain copyright assertions by specific individuals involved with html5lib. Those have been retained where appropriate.