Slimdown - A simple regex-based Markdown parser.

Slimdown.md

Slimdown

This project has moved to github.com/jbroadway/slimdown

A very basic regex-based Markdown parser. Supports the following elements (and can be extended via Slimdown::add_rule()):

• Headers
• Links
• Bold
• Emphasis
• Deletions
• Quotes
• Inline code
• Blockquotes
• Ordered/unordered lists

Usage

Here is the general use case:

<?php

require_once ('Slimdown.php');

echo Slimdown::render (
	"# Page title\n\nAnd **now** for something _completely_ different."
);

?>

Adding rules

A simple rule to convert :) to an image:

<?php

require_once ('Slimdown.php');

Slimdown::add_rule ('/(\W)\:\)(\W)/', '\1<img src="smiley.png" />\2');

echo Slimdown::render ('Know what I\'m sayin? :)');

?>

In this example, we add GitHub-style internal linking (e.g., [[Another Page]]).

<?php

require_once ('Slimdown.php');

function mywiki_internal_link ($title) {
	return sprintf (
		'<a href="%s">%s</a>',
		preg_replace ('/[^a-zA-Z0-9_-]+/', '-', $title),
		$title
	);
}

Slimdown::add_rule ('/\[\[(.*?)\]\]/e', 'mywiki_internal_link (\'\\1\')');

echo Slimdown::render ('Check [[This Page]] out!');

?>

A longer example

<?php

require_once ('Slimdown.php');

echo Slimdown::render ("# Title

And *now* [a link](http://www.google.com) to **follow** and [another](http://yahoo.com/).

* One
* Two
* Three

## Subhead

One **two** three **four** five.

One __two__ three _four_ five __six__ seven _eight_.

1. One
2. Two
3. Three

More text with `inline($code)` sample.

> A block quote
> across two lines.

More text...");

?>

Slimdown.php

<?php

/**
 * Slimdown - A very basic regex-based Markdown parser. Supports the
 * following elements (and can be extended via Slimdown::add_rule()):
 *
 * - Headers
 * - Links
 * - Bold
 * - Emphasis
 * - Deletions
 * - Quotes
 * - Inline code
 * - Blockquotes
 * - Ordered/unordered lists
 * - Horizontal rules
 *
 * Author: Johnny Broadway <[email protected]>
 * Website: https://gist.github.com/jbroadway/2836900
 * License: MIT
 */
class Slimdown {
	public static $rules = array (
		'/(#+)(.*)/' => 'self::header',                           // headers
		'/\[([^\[]+)\]\(([^\)]+)\)/' => '<a href=\'\2\'>\1</a>',  // links
		'/(\*\*|__)(.*?)\1/' => '<strong>\2</strong>',            // bold
		'/(\*|_)(.*?)\1/' => '<em>\2</em>',                       // emphasis
		'/\~\~(.*?)\~\~/' => '<del>\1</del>',                     // del
		'/\:\"(.*?)\"\:/' => '<q>\1</q>',                         // quote
		'/`(.*?)`/' => '<code>\1</code>',                         // inline code
		'/\n\*(.*)/' => 'self::ul_list',                          // ul lists
		'/\n[0-9]+\.(.*)/' => 'self::ol_list',                    // ol lists
		'/\n(&gt;|\>)(.*)/' => 'self::blockquote ',               // blockquotes
		'/\n-{5,}/' => "\n<hr />",                                // horizontal rule
		'/\n([^\n]+)\n/' => 'self::para',                         // add paragraphs
		'/<\/ul>\s?<ul>/' => '',                                  // fix extra ul
		'/<\/ol>\s?<ol>/' => '',                                  // fix extra ol
		'/<\/blockquote><blockquote>/' => "\n"                    // fix extra blockquote
	);

	private static function para ($regs) {
		$line = $regs[1];
		$trimmed = trim ($line);
		if (preg_match ('/^<\/?(ul|ol|li|h|p|bl)/', $trimmed)) {
			return "\n" . $line . "\n";
		}
		return sprintf ("\n<p>%s</p>\n", $trimmed);
	}

	private static function ul_list ($regs) {
		$item = $regs[1];
		return sprintf ("\n<ul>\n\t<li>%s</li>\n</ul>", trim ($item));
	}

	private static function ol_list ($regs) {
		$item = $regs[1];
		return sprintf ("\n<ol>\n\t<li>%s</li>\n</ol>", trim ($item));
	}

	private static function blockquote ($regs) {
		$item = $regs[2];
		return sprintf ("\n<blockquote>%s</blockquote>", trim ($item));
	}

	private static function header ($regs) {
		list ($tmp, $chars, $header) = $regs;
		$level = strlen ($chars);
		return sprintf ('<h%d>%s</h%d>', $level, trim ($header), $level);
	}

	/**
	 * Add a rule.
	 */
	public static function add_rule ($regex, $replacement) {
		self::$rules[$regex] = $replacement;
	}

	/**
	 * Render some Markdown into HTML.
	 */
	public static function render ($text) {
		$text = "\n" . $text . "\n";
		foreach (self::$rules as $regex => $replacement) {
			if (is_callable ( $replacement)) {
				$text = preg_replace_callback ($regex, $replacement, $text);
			} else {
				$text = preg_replace ($regex, $replacement, $text);
			}
		}
		return trim ($text);
	}
}

Thanks for sharing! Although marked supports all Markdown features, I did convert (and slightly improve) this version to TypeScript (~2kb vs 23kb). You can find it on GitHub, on NPM, and on the playground.

My improvements are mainly related to adding support for images, tables and codeblocks, and some other fixes. Clearly I did mention you as the original author.

Hi brother, how can I render HTML to markdown with your script?

You should be able to just say echo Slimdown::render($my_text)

To allow multiline <code> just add:

'/```(.*)```/s' => 'self::code_parse',

to the $rules array (at the beginning), then add the following function to the main class:

private static function code_parse ($regs) {
    $item = $regs[1];
    $item = htmlentities($item);
    $item = str_replace("\n\n", '<br>', $item);
    $item = str_replace("\n", '<br>', $item);
    while (mb_substr($item, 0, 4) === '<br>') {
        $item = mb_substr($item, 4);
    }
    while (mb_substr($item, -4) === '<br>') {
        $item = mb_substr($item, 0, -4);
    }
    return sprintf ("<code>%s</code>", trim($item));
}

Also, your para function should look like this:

private static function para ($regs) {
    $line = $regs[1];
    $trimmed = trim ($line);
    if (preg_match ('/^<\/?(ul|ol|li|h|p|bl|code)/', $trimmed)) {         // `code` added here
        return "\n" . $line . "\n";
    }
    if (!empty($trimmed)){
        return sprintf ("\n<p>%s</p>\n", $trimmed);
    }else{
        return sprintf($trimmed);
    }
}

@gre-dev thanks!

I just moved this over to a proper repository and incorporated your code block support along with a few other fixes 😄

The new home for Slimdown is now:

https://github.com/jbroadway/slimdown

Cheers!

Thank you!

How would I go about making a list like
1
1a
1b

How would I go about making a list like 1 1a 1b

This is supported in markdown. Basically, markdown converts a list to a HTML <ol> (ordered list) element, which does not support your requirement.