The AttributesExtension allows HTML attributes to be added from within the document.

Attribute Syntax

The basic syntax was inspired by Kramdown’s Attribute Lists feature.

You can assign any attribute to a block-level element. Just directly prepend or follow the block with a block inline attribute list. That consists of a left curly brace, optionally followed by a colon, the attribute definitions and a right curly brace:

> A nice blockquote
{: title="Blockquote title"}

This results in the following output:

<blockquote title="Blockquote title">
<p>A nice blockquote</p>

CSS-selector-style declarations can be used to set the id and class attributes:

{#id .class}
## Header


<h2 class="class" id="id">Header</h2>

As with a block-level element you can assign any attribute to a span-level elements using a span inline attribute list, that has the same syntax and must immediately follow the span-level element:

This is *red*{style="color: red"}.


<p>This is <em style="color: red">red</em>.</p>


This extension is bundled with league/commonmark. This library can be installed via Composer:

composer require league/commonmark

See the installation section for more details.


Configure your Environment as usual and simply add the AttributesExtension:

use League\CommonMark\Environment\Environment;
use League\CommonMark\Extension\Attributes\AttributesExtension;
use League\CommonMark\Extension\CommonMark\CommonMarkCoreExtension;
use League\CommonMark\MarkdownConverter;

// Define your configuration, if needed
$config = [];

// Configure the Environment with all the CommonMark parsers/renderers
$environment = new Environment($config);
$environment->addExtension(new CommonMarkCoreExtension());

// Add this extension
$environment->addExtension(new AttributesExtension());

// Instantiate the converter engine and start converting some Markdown!
$converter = new MarkdownConverter($environment);
echo $converter->convert('# Hello World!');

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