Yet another syntax highlighter for PHP

0.8.4 2020-11-01 14:21 UTC



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stability: stable stability: unstable

Yet another Syntax Highlighter in PHP meant to be as extensible and easy to use as it only can, but with performance in mind.

You can try it live with most recent version on


Name "KeyLighter" is inspired by Key Light concept in photography and cinematography.

The key light is the first and usually most important light that a photographer, cinematographer, lighting cameraman, or other scene composer will use in a lighting setup. The purpose of the key light is to highlight the form and dimension of the subject.

KeyLighter is supposed to do the same thing - for code.


$ composer require kadet/keylighter

To use KeyLighter you just need PHP 5.5 or later, no special extensions required.

Global installation

It's possible to install KeyLighter as a global composer library

$ composer global require kadet/keylighter

Then you can use builtin simple cli highlighting app:

$ keylighter [command = highlight] [-l|--language [LANGUAGE]] [-f|--format [FORMAT]] [-d|--debug [DEBUG]] [--]  <path>...

If you want pipe into KeyLighter just specify php://stdin as path. You can use list command to see all available commands, and --help argument for detailed help. You don't have to specify highlight command explicitly.


You're using PowerShell on Windows? Cool! KeyLighter comes with integrated PowerShell module that makes CLI usage even better. Just import module (For example in profile), and you're ready to go.

PS> Import-Module "${env:APPDATA}\Composer\vendor\kadet\keylighter\bin\KeyLighter.psd1"

To use autocompletion features you will need PowerShell v5 (Comes with windows 10) or install TabExpansion++ Module.

Powershell Support

Why KeyLighter?

Simple to use

use Kadet\Highlighter\Language;

echo \Kadet\Highlighter\highlight($source, new Language\Php(), $formatter);
// or
echo \Kadet\Highlighter\KeyLighter::get()->highlight($source, new Language\Php(), $formatter);
// or
$keylighter = new \Kadet\Highlighter\KeyLighter([options]);
echo $keylighter->highlight($source, new Language\Php(), $formatter);

You can find all available languages here and formatters here.

It works on CLI! And more!

KeyLighter was originally designed as CLI highlighter for my own usage, but then I decided that it should be able to generate any possible output, currently supported:

Cli \Kadet\Highlighter\Formatter\CliFormatter


It can even be styled, default styles are stored in Styles\Cli\Default.php, but you can just pass additional argument into constructor:

new \Kadet\Highlighter\Formatter\CliFormatter([
    'string'      => ['color' => 'green'],
    'keyword'     => ['color' => 'yellow'],

HTML \Kadet\Highlighter\Formatter\HtmlFormatter


Every token is placed inside it's own span so it can be easily styled with css.

<span class="variable">$maxOption</span>
pre > span.variable { color: #F7750D; }

Your own?

It's easy to write your own formatters. Documentation coming soon.

Context sensitive

Some of tokens are valid in some contexts, some are not. This library is context sensitive and you can define when they are valid.

In this case, context mean just "inside of other token", for example lets assume that string token is defined as everything from " to the next " and keyword is defined as 'sit' substring.

 string:start      keyword:start
"Lorem ipsum dolor sit amtet"
         keyword:end        string:end

Token tree:           Token.pos
string:start         0
    keyword:start    21
    keyword:end      23
string:end           30

So as you can see keyword is inside of string, and therefore is not valid and should be deleted. You can define tokens valid only in some context, or invalid in other.

Oh, and token names cascade, it means that string.single is string, but string is necessarily not string.single.

Write your own language definitions easily

It's possible to easily extend KeyLighter with new languages, more detailed documentation coming soon.

For example XML definition looks like this:

class Xml extends GreedyLanguage
    const IDENTIFIER = '(?P<namespace>[\w\.-]+:)?(?P<name>[\w\.-]+)';

     * Tokenization rules
    public function setupRules()
            ''  => [
                new OpenRule(new RegexMatcher('/(<\w+)[:\/>:\s]/')),
                new CloseRule(new SubStringMatcher('>'), ['context' => ['!string', '!comment']])
            'tag.close' => new Rule(new RegexMatcher('/(<\/(?:\w+:)?(?:[\w\.]+)>)/')),

            'symbol.tag' => new Rule(new RegexMatcher('/<\\/?' . self::IDENTIFIER . '/', [
                'name'      => Token::NAME,
                'namespace' => '$.namespace'
            ]), ['context' => ['tag', '!string']]),

            'symbol.attribute' => new Rule(new RegexMatcher('/' . self::IDENTIFIER . '=/', [
                'name'      => Token::NAME,
                'namespace' => '$.namespace'
            ]), ['context' => ['tag', '!string']]),

            'constant.entity' => new Rule(new RegexMatcher('/(&(?:\#\d+|[a-z])+;)/si')),

            'comment' => new Rule(new CommentMatcher(null, [['<!--', '-->']])),
            'string'  => CommonFeatures::strings(['single' => '\'', 'double' => '"'], ['context' => ['tag']]),

    /** {@inheritdoc} */
    public function getIdentifier()
        return 'xml';

I will try to write as many definitions as I only can, but any PRs are welcome.

Embedding languages

Many languages can be used simultaneously, css or js inside html, sql in php and so on. KeyLighter can handle and highlight embedded languages without any problem.

Embedded languages

Fast Optimized for php7.0

Even though it wasn't supposed to be fastest code highlighter in PHP it is still quite fast, up to few times faster than GeSHi. It performs best on PHP 7 (more than 2x faster than GeSHi in every case).

Testing Code Coverage

KeyLighter uses phpunit for testing:

$ phpunit


There are still few things to do, you can find all on trello.


See for details.


For Maciej, Maciej and Monika for all support, moral too.