Languages

The default registry contains 27 languages. Pass the identifier in the Identifier column to Highlighter::highlight().

Identifiers are case-insensitive after trimming, but there are no short aliases. Use javascript, not js; typescript, not ts; bash, not sh; yaml, not yml; and csharp, not cs.

Read Embedded languages for HTML, SVG, Markdown, and Twig delegation.

Default registry

Language	Identifier	Category	Typical extension	Parsing focus	Example
Bash	bash	Shell	.sh	Shell keywords, built-ins, variables, strings, and here-docs	Source
C#	csharp	Programming	.cs	Two-pass definitions, calls, and type references	Source
CSS	css	Stylesheet	.css	Selectors, declarations, values, comments, and at-rules	Source
Diff	diff	Change	.diff	File headers, hunks, added lines, and removed lines	Source
Dockerfile	dockerfile	Build	Dockerfile	Instructions, modifiers, variables, strings, and comments	Source
dotenv	dotenv	Configuration	.env	Assignments, export, references, values, and comments	Source
Go	go	Programming	.go	Two-pass functions, methods, receivers, and type references	Source
HTML	html	Markup	.html	Tags, attributes, text, and embedded CSS or JavaScript	Source
HTTP	http	Protocol	.http	Request or response lines, headers, and body text	Source
INI	ini	Configuration	.ini	Sections, assignments, typed values, references, and comments	Source
Java	java	Programming	.java	Two-pass definitions, calls, types, and brace context	Source
JavaScript	javascript	Programming	.js	Declarations, calls, literals, templates, and regular expressions	Source
JSON	json	Data	.json	Object keys, strings, numbers, booleans, and null	Source
Makefile	makefile	Build	.mk	Targets, dependencies, recipes, variables, and directives	Source
Markdown	markdown	Markup	.md	Blocks, inline markup, and registered fenced languages	Source
PHP	php	Programming	.php	Two-pass semantic definitions, calls, types, and variables	Source
Python	python	Programming	.py	Two-pass function and class definitions, calls, and references	Source
Ruby	ruby	Programming	.rb	Two-pass definitions, calls, constants, and variables	Source
Rust	rust	Programming	.rs	Two-pass definitions, calls, types, lifetimes, and macros	Source
SCSS	scss	Stylesheet	.scss	CSS plus variables, nesting, mixins, and interpolation	Source
SQL	sql	Data	.sql	Keywords, functions, identifiers, literals, and comments	Source
SVG	svg	Markup	.svg	XML-style markup plus embedded CSS or JavaScript	Source
Swift	swift	Programming	.swift	Two-pass definitions, calls, types, attributes, and variables	Source
Twig	twig	Templating	.twig	Twig expressions and tags with embedded HTML by default	Source
TypeScript	typescript	Programming	.ts	JavaScript plus types, interfaces, enums, and decorators	Source
XML	xml	Markup	.xml	Tags, attributes, processing instructions, and CDATA	Source
YAML	yaml	Data	.yaml	Mappings, sequences, anchors, aliases, values, and comments	Source

The source files above are the canonical compact documentation examples. See Examples for generated previews.

PHP snippets without an opening tag

Selecting php parses PHP from the first byte, including when the opening tag is omitted:

$html = $highlighter->highlight(
    '$total = array_sum($prices);',
    'php',
);

Any synthetic context required by PHP's native tokenizer is absent from the returned stream, so text, byte offsets, lines, and columns describe the exact source supplied by the caller.

The historical php-snippet identifier remains a compatibility alias for php; it is not a 28th registered language. New code should use php.

Register a custom language

Custom parsers implement LanguageInterface and return a ParsedStream:

use Alto\Code\Highlight\Language\LanguageInterface;
use Alto\Code\Highlight\Parser\ParsedStream;
use Alto\Code\Highlight\Parser\ParsedToken;
use Alto\Code\Highlight\Scope;

final class MyLanguage implements LanguageInterface
{
    public function getIdentifier(): string
    {
        return 'my-language';
    }

    public function parse(string $code): ParsedStream
    {
        return new ParsedStream([
            new ParsedToken($code, Scope::MarkupText),
        ]);
    }
}

$highlighter->registerLanguage(new MyLanguage());

Registering an existing identifier replaces that parser on the highlighter instance. Theme authors style the generic semantic scopes emitted by parsers; see Creating a theme.

Extension contract

Custom parsers implement LanguageInterface and return a ParsedStream made of ParsedToken values. StreamBuilder, TokenType, and Scope are supported building blocks. Languages::getDefaultLanguages() returns the built-in registry.

Embedded parsers use EmbeddedLanguageCapable, EmbeddedLanguageContext, and the public types under Alto\Code\Highlight\Embedded. Their documented constructors and methods follow the same compatibility promise described in Compatibility.