Markdown is one of the most popular markup languages on the web. Unfortunately, with no standard specification, every implementation works differently, producing varying results across different platforms. The CommonMark specification fixes this by providing an unambiguous syntax specification and a comprehensive suite of tests. In this session you'll learn about this standard and how to integrate the league/commonmark parser into their PHP applications. We'll also cover how to customize the library to implement new features like custom Markdown syntax or advanced renderers.

1. CommonMark
Markdown done right
Colin O’Dell
@colinodell

2. COLIN O’DELL
Creator & Maintainer of league/commonmark
Lead Web Developer at Unleashed Technologies
Author of PHP 7 Migration Guide e-book
@colinodel
l

3. LEAGUE/COMMONMARK
A well-written, super-configurable
Markdown parser for PHP based on the
CommonMark spec.
@colinodel
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4. ORIGINS OF MARKDOWN
Created in March 2004 by John Gruber
Informal plain-text formatting language
Converts readable text to valid (X)HTML
Primary goal - readability
@colinodel
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5. HISTORY OF MARKDOWN
Hello ZendCon!
--------------
Markdown is **awesome**!
1. Foo
2. Bar
3. Baz
Wikipedia entry:
<https://en.wikipedia.org/wiki/Markdown> @colinodel
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6. WHY IS IT SUCCESSFUL?
1. Syntax is visually-similar to the resulting
markup
2. Non-strict, forgiving parsing
3. Easily adaptable for different uses
@colinodel
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7. 68+ DIFFERENT FLAVORS
Source: https://github.com/markdown/markdown.github.com/wiki/Implementations
Actuarius
Blackfriday
BlueCloth
BlueFeather
cebe/markdown
CocoaMarkdown
CommonMark
Discount
ffi-sundown
GHMarkdownParser
Goskirt
Hoedown
Hoep
Knockoff
kramdown
Laika
libpandoc
Lowdown
lua-discount
Lunamark
markdown
markdown-clj
markdown-js
markdown-oo-php
markdown.bash
markdown.lua
markdown.pl
markdown4j
MarkdownDeep
MarkdownJ
MarkdownPapers
MarkdownSharp
marked
Maruku
md2html.awk
Misaka
Mistune
MMMarkdown
MoonShine
MultiMarkdown
node-discount
node-markdown
node-multimarkdown
OMD
Pandoc
Parsedown
Parsedown Extra
peg-markdown
peg-multimarkdown & fork
pegdown
PHP Markdown
PHP Markdown Extra
PHP-Sundown
Python-Discount
python-hoedown
Python-Markdown
Python-Markdown2
RDiscount
Redcarpet
RoboSkirt
Showdown
Sundown
Sundown HS
Sundown.net
text-markdown
texts.js
Txtmark
upskirt.go
@colinodel
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8. https://xkcd.com/927/
@colinodel
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9. WHY IS IT NEEDED?
*I love Markdown*
<p><em>I love Markdown</em></p>
@colinodel
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10. WHY IS IT NEEDED?
*I *love* Markdown*
@colinodel
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11. WHY IS IT NEEDED? Source: http://johnmacfarlane.net/babelmark2/

12. 30%
WHY IS IT NEEDED?
*I *love* Markdown*
<p><em>I <em>love</em> Markdown</em></p>
*I *love* Markdown*
<p><em>I </em>love<em> Markdown</em></p>
*I *love* Markdown*
<p><em>I *love</em> Markdown*</p>
15%
33%
Source: http://johnmacfarlane.net/babelmark2/
@colinodel
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13. WHY IS IT NEEDED?
1. > Hello
World!
------
Source: http://johnmacfarlane.net/babelmark2/

14. WHY IS IT NEEDED?
1. > Hello
World!
------
Source: http://johnmacfarlane.net/babelmark2/

15. WHY IS IT NEEDED?
1. > Hello
World!
------
Source: http://johnmacfarlane.net/babelmark2/

16. WHY IS IT NEEDED?
1. > Hello
World!
------
Source: http://johnmacfarlane.net/babelmark2/

17. WHY IS IT NEEDED?
1. > Hello
World!
------
Source: http://johnmacfarlane.net/babelmark2/

18. COMMONMARK IS…
A strongly defined, highly compatible specification of Markdown.
Written by people from Github, StackOverflow, Reddit, and others.
Spec includes:
 Strict rules (precedence, parsing order, handling edge cases)
 Specific definitions (ex: “whitespace”, “punctuation”)
 624 examples
@colinodel
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23. FEATURES
 100% compliance with the CommonMark spec
 Easy to implement
 Easy to customize
 Well-tested
 Decent performance
 (Relatively) stable
@colinodel
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24. FEATURES
 100% compliance with the CommonMark spec
 Easy to implement
 Easy to customize
 Well-tested
 Decent performance
 (Relatively) stable
@colinodel
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25. ADDING LEAGUE/COMMONMARK
$ composer require league/commonmark:^0.15
<?php
$converter = new CommonMarkConverter();
echo $converter->convertToHtml('Hello **ZendCon!**');
@colinodel
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26. INTEGRATIONS

27. FEATURES
 100% compliance with the CommonMark spec
 Easy to implement
 Easy to customize
 Well-tested
 Decent performance
 (Relatively) stable
@colinodel
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28. FEATURES
 100% compliance with the CommonMark spec
 Easy to implement
 Easy to customize
 Well-tested
 Decent performance
 (Relatively) stable
@colinodel
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29. CONVERSION PROCESS
<http://www.zendcon.com>
<a href="http://www.zendcon.com">
http://www.zendcon.com
</a>
@colinodel
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30. CONVERSION PROCESS
<http://www.zendcon.com>
Markdow
n
Parse
@colinodel
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31. <document>
<paragraph>
<link destination="http://www.zendcon.com">
<text>http://www.zendcon.com</text>
</link>
</paragraph>
</document>
CONVERSION PROCESS
Markdow
n
AST RenderParse
@colinodel
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32. CONVERSION PROCESS
<a href="http://www.zendcon.com">
http://www.zendcon.com
</a>
Markdow
n
AST HTMLRenderParse
@colinodel
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33. CONVERSION PROCESS
Markdow
n
AST HTMLRenderParse
Add your own custom parser, processor, or renderer
@colinodel
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34. EXAMPLE 1: CUSTOM PARSER
<http://www.zendcon.com>
<a href="http://www.zendcon.com">
http://www.zendcon.com
</a>
<@colinodell>
<a href="https://twitter.com/colinodell">
@colinodell
</a>
@colinodel
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35. class TwitterUsernameAutolinkParser extends AbstractInlineParser {
public function getCharacters() {
return ['<'];
}
public function parse(InlineParserContext $inlineContext) {
// TODO
}
}
@colinodel
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36. CURSOR
Learning CommonMark with <@colinodell>!
public function getCharacters()
{
return ['<'];
}
@colinodel
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37. class TwitterUsernameAutolinkParser extends AbstractInlineParser {
public function getCharacters() {
return ['<'];
}
public function parse(InlineParserContext $inlineContext) {
$cursor = $inlineContext->getCursor();
}
}
@colinodel
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38. CURSOR
Learning CommonMark with <@colinodell>!
getCharacter()
getFirstNonSpaceCharacter(
)
getRemainder()
getLine()
getPosition()
advance()
advanceBy($count)
advanceBySpaceOrTab()
advanceWhileMatches($char
)
advanceToFirstNonSpace()
isIndented()
isAtEnd()
match($regex)
peek($count)
@colinodel
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39. CURSOR
Learning CommonMark with <@colinodell>!
getCharacter()
getFirstNonSpaceCharacter(
)
getRemainder()
getLine()
getPosition()
advance()
advanceBy($count)
advanceBySpaceOrTab()
advanceWhileMatches($char
)
advanceToFirstNonSpace()
isIndented()
isAtEnd()
match($regex)
peek($count)
@colinodel
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40. CURSOR
Learning CommonMark with <@colinodell>!
getCharacter()
getFirstNonSpaceCharacter(
)
getRemainder()
getLine()
getPosition()
advance()
advanceBy($count)
advanceBySpaceOrTab()
advanceWhileMatches($char
)
advanceToFirstNonSpace()
isIndented()
isAtEnd()
match($regex)
peek($count)
/^<@[A-Za-z0-9_]+>/
@colinodel
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41. CUSTOMIZING LEAGUE/COMMONMARK
class TwitterUsernameAutolinkParser extends AbstractInlineParser {
public function getCharacters() {
return ['<'];
}
public function parse(InlineParserContext $inlineContext) {
$cursor = $inlineContext->getCursor();
if ($match = $cursor->match('/^<@[A-Za-z0-9_]+>/')) {
// Remove the starting '<@' and ending '>' that were matched
$username = substr($match, 2, -1);
$profileUrl = 'https://twitter.com/' . $username;
$link = new Link($profileUrl, '@'.$username);
$inlineContext->getContainer()->appendChild($link);
return true;
}
return false;
}
}
@colinodel
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42. $environment = Environment::createCommonMarkEnvironment();
$environment->addInlineParser(
new TwitterHandleParser()
);
$converter = new CommonMarkConverter($environment);
$html = $converter->convertToHtml(
"Follow <@colinodell> on Twitter!"
);
@colinodel
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43. EXAMPLE 2: CUSTOM AST PROCESSOR
<document>
<paragraph>
<link destination="http://www.zendcon.com">
<text>http://www.zendcon.com</text>
</link>
</paragraph>
</document>
<document>
<paragraph>
<link destination="https://bit.ly/foo">
<text>http://www.zendcon.com</text>
</link>
</paragraph>
</document>
@colinodel
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44. class ShortenLinkProcessor implements DocumentProcessorInterface {
public function processDocument(Document $document) {
$walker = $document->walker();
while ($event = $walker->next()) {
if ($event->isEntering() && $event->getNode() instanceof Link) {
/** @var Link $linkNode */
$linkNode = $event->getNode();
$originalUrl = $linkNode->getUrl();
$shortUrl = $this->bitly->shorten($originalUrl);
$linkNode->setUrl($shortUrl);
}
}
}
}
@colinodel
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45. $environment = Environment::createCommonMarkEnvironment();
$environment->addDocumentProcessor(
new ShortenLinkProcessor()
);
$converter = new CommonMarkConverter($environment);
$html = $converter->convertToHtml(
"Schedule: <http://www.zendcon.com/schedule>"
);
EXAMPLE 2: CUSTOM AST PROCESSOR
@colinodel
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46. EXAMPLE 3: CUSTOM RENDERER
<document>
<paragraph>
<text>Hello World!</text>
</paragraph>
<thematic_break />
</document>
<p>Hello World!</p>
<hr />
<p>Hello World!</p>
<img src="hr.png" />
@colinodel
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47. EXAMPLE 3: CUSTOM RENDERER
class ImageHorizontalRuleRenderer implements BlockRendererInterface {
public function render(...) {
return new HtmlElement('img', ['src' => 'hr.png']);
}
}
@colinodel
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48. $environment = Environment::createCommonMarkEnvironment();
$environment->addBlockRenderer(
LeagueCommonMarkBlockElementThematicBreak::class,
new ImageHorizontalRuleRenderer()
);
$converter = new CommonMarkConverter($environment);
$html = $converter->convertToHtml("Hello World!nn-----");
EXAMPLE 3: CUSTOM RENDERER
@colinodel
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49. BUNDLING INTO AN EXTENSION
class MyCustomExtension extends Extension {
public function getInlineParsers() {
return [new TwitterUsernameAutolinkParser()];
}
public function getDocumentProcessors() {
return [new ShortenLinkProcessor()];
}
public function getBlockRenderers() {
return [new ImageHorizontalRuleRenderer()];
}
}
@colinodel
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50. BUNDLING INTO AN EXTENSION
$environment = Environment::createCommonMarkEnvironment();
$environment->addExtension(new MyCustomExtension());
$converter = new CommonMarkConverter($environment);
$html = $converter->convertToHtml("...");
@colinodel
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51. FEATURES
 100% compliance with the CommonMark spec
 Easy to implement
 Easy to customize
 Well-tested
 Decent performance
 (Relatively) stable
@colinodel
l

52. FEATURES
 100% compliance with the CommonMark spec
 Easy to implement
 Easy to customize
 Well-tested
 Decent performance
 (Relatively) stable
@colinodel
l

53. WELL-TESTED
 94% code coverage
 Functional tests
 All 624 spec examples
 Library of regression tests
 Unit tests
 Cursor
 Environment
 Utility classes
@colinodel
l

54. FEATURES
 100% compliance with the CommonMark spec
 Easy to implement
 Easy to customize
 Well-tested
 Decent performance
 (Relatively) stable
@colinodel
l

55. FEATURES
 100% compliance with the CommonMark spec
 Easy to implement
 Easy to customize
 Well-tested
 Decent performance
 (Relatively) stable
@colinodel
l

56. PERFORMANCE
0 20 40 60 80
Parsedown
cebe/markdown gfm
PHP Markdown Extra
league/commonmark
Time (ms)
league/commonmark is ~22-24ms slower
PHP 5.6 PHP 7.1
Tips:
• Choose library based on your
needs
• Cache rendered HTML (100%
boost)
• Use PHP 7 (50% boost)
• Optimize custom functionality
@colinodel
l

57. FEATURES
 100% compliance with the CommonMark spec
 Easy to implement
 Easy to customize
 Well-tested
 Decent performance
 (Relatively) stable
@colinodel
l

58. FEATURES
 100% compliance with the CommonMark spec
 Easy to implement
 Easy to customize
 Well-tested
 Decent performance
 (Relatively) stable
@colinodel
l

59. STABILITY
 Current version: 0.15.6
 Conforms to CommonMark spec 0.28
 1.0.0 will be released once CommonMark spec is 1.0
 No major stability issues
 Backwards Compatibility Promise:
 No BC breaks to CommonMarkConverter class in 0.x
 Other BC breaks are documented (see UPGRADING.md)
@colinodel
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60. FEATURES
 100% compliance with the CommonMark spec
 Easy to implement
 Easy to customize
 Well-tested
 Decent performance
 (Relatively) stable
@colinodel
l

61. Installation & Documentation:
http://github.com/thephpleague/commonmark
Learn More About CommonMark:
http://commonmark.org
Slides / Feedback:
https://joind.in/talk/8da74
@colinodell