html2markdown for PHP

An HTML-to-markdown conversion tool for PHP by @nickcernis

Version 1.0.1
Requires PHP 5
Licensed under The MIT license: http://www.opensource.org/licenses/mit-license.php

###Instructions

Include html2markdown.php:

require_once( dirname( __FILE__) . '/html2markdown.php' );

Call html2markdown() on your valid, slash-stripped HTML code:

$markdown = html2markdown($html);

The $markdown string now contains the markdowned version of your HTML.

The included demo.php file contains an HTML->markdown conversion form for testing.

###Limitations

• Chokes on malformed HTML. i.e. unclosed tags. Am considering a cleanup function to check for simple errors with an off switch for projects that perform their own reformatting, like WordPress. At present, you must nest <code> blocks inside <p> or <pre>, for example.
• Markdown Extra, MultiMarkdown and other variants aren't supported; just Markdown.

###Bugs

• Nested lists and lists with multiple paragraphs aren't converted correctly.
• Lists inside blockquotes aren't converted correctly.

###Style notes

• SETEX (underlined) headers are the default for H1 and H2. Change the HTML2MD_HEADER_STYLE constant to "ATX" if you want # H1 and ## H2 style tags instead.
• Reference-style labels (with src and href links in the footnotes) are not used. Links and images are all referenced inline.
• Blockquotes aren't line wrapped (makes them easier to edit).

###Architecture notes

html2markdown is about 450 lines. It's a single file with no dependencies. It uses native DOM manipulation libraries (DOMDocument), not regex voodoo, to convert code. Bug fixes and improvements are welcome.

###Contributors

My thanks to unlight and iamthes for their contributions.

###How it works html2markdown creates a DOM tree from the supplied HTML, walks through the tree, and converts each node to a text node, starting from the most deeply nested node and working inwards towards the root node.

###TO-DO

• Support for nested lists and lists inside blockquotes.

###Trying to convert Markdown to HTML?

Use PHP Markdown from Michel Fortin.