Pure PHP JavaScript engine

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What is Phasis?

Phasis lexes, parses, and executes ECMAScript in pure PHP. No exec('node …'), no FFI, no binary extensions beyond ext-mbstring (always shipped) and ext-bcmath (shipped by default on every mainstream PHP build for BigInt arithmetic and integer-precision number handling). ext-intl is optional — Phasis runs without it, but the Intl.* APIs (Collator, NumberFormat, DateTimeFormat, …) and non-ISO Temporal calendars require it. The whole engine ships as a Composer package and runs anywhere PHP 8.2+ runs.

The problem: PHP applications that need to run user-supplied JavaScript — templating engines, SSR shims, validation rules, content sandboxes, headless test runners — usually shell out to Node.js or skip the feature. Either path adds operational complexity: a second runtime, a serialization boundary, a network of subprocess pipes, and a hostile deployment story for shared hosting.

Phasis solves this by implementing the ECMAScript language and standard library natively in PHP:

• Full ES2024+ language surface (classes, async/await, generators, decorators, top-level await, ES modules)
• Complete standard library (Array, String, Object, Math, JSON, Date, RegExp, Map, Set, Promise, Proxy, Reflect, Symbol, BigInt, TypedArray, Temporal, Intl)
• Web Platform Pack: URL, URLSearchParams, TextEncoder/TextDecoder, atob/btoa, structuredClone, performance, DOMException
• Fetch Pack: fetch, Request, Response, Headers, Body, AbortController/AbortSignal, Blob/File, FormData, EventTarget/Event, full WHATWG Streams, navigator
• Crypto: crypto.getRandomValues, crypto.randomUUID, full SubtleCrypto (SHA family, HMAC, AES-GCM/CBC/CTR, RSA-OAEP/PSS/PKCS1, ECDSA, ECDH, HKDF, PBKDF2)
• WebSocket (RFC 6455 + replaceable transport), XMLHttpRequest (layered over fetch), and a real event loop (setTimeout / setInterval / queueMicrotask, plus Stage-3 AsyncContext)
• Direct PHP↔JS interop — share objects without serialization, bind PHP callables as JS functions
• 100 % of the official test262 suite passes — ECMAScript conformance, every category, no skips
• 100 % of imported Web Platform Tests pass across fetch, headers, blob, abort, streams, encoding, URL, structured-clone, hr-time, and atob

Quick Start

composer require phasis/phasis

use Phasis\Engine;

$engine = new Engine();

// Evaluate an expression
$engine->eval('1 + 2 * 3');                  // 7

// Run a file
$engine->execFile('/path/to/script.js');

// Bridge a PHP value into JS
$engine->setGlobal('config', ['debug' => true]);
$engine->eval('console.log(config.debug)');  // true

// Expose a PHP closure as a JS function
$engine->setGlobal('greet', fn(string $name) => "Hello, $name");
$engine->eval('greet("world")');             // "Hello, world"

// Share a PHP object by reference
class Counter { public int $value = 0; }
$counter = new Counter();
$engine->setGlobal('counter', $counter);
$engine->eval('counter.value++');
echo $counter->value;                         // 1

// Call JS functions from PHP
$engine->eval('function add(a, b) { return a + b; }');
echo $engine->call('add', 2, 3);              // 5

CLI

Phasis ships two CLI binaries:

# Run a JavaScript file
./vendor/bin/phasis script.js

# Evaluate an expression
./vendor/bin/phasis -e '[1, 2, 3].map(x => x * x)'

# Interactive REPL
./vendor/bin/phasis --repl

# Dump the AST
./vendor/bin/phasis --ast script.js

# Run the official test262 conformance suite
./vendor/bin/test262 --category built-ins/Array
./vendor/bin/test262 --jobs 4

Testing

Phasis is verified against Node.js (V8) and the official ECMAScript test262 conformance suite.

# Unit tests
composer test

# PHPStan (level 6, zero errors)
composer analyse

# Code standards
composer cs

# Oracle regression (scenarios with Node.js as the ground truth)
./bin/test-regression

# Full quality gate (PHPStan + PHPCS + PHPUnit + oracle)
./bin/verify-all

# test262 conformance sample
./bin/test262 --category built-ins/Array --jobs 4

The complete test262 matrix runs in CI on every push. Compliance numbers are committed to COMPAT.md after each run.

Compatibility

Engine	test262 pass rate
V8 (Chrome / Node)	99.8 %
SpiderMonkey (Firefox)	99.6 %
JavaScriptCore (Safari)	99.4 %
QuickJS	~97 %
Hermes (React Native)	~95 %
Phasis	100 %

Every test in the official suite passes, every category. See COMPAT.md for the latest snapshot.

Performance

Phasis is a tree-walking interpreter with an opportunistic bytecode VM. Expect ~100× the runtime of V8 on dispatch-bound JS — the trade-off is zero dependencies, pure PHP, and host-controlled execution. For embedding workloads where you run user-supplied logic on PHP data, that ceiling rarely matters.

Current microbench numbers are committed in BENCH.md after each bench workflow run.

Documentation

Full documentation lives at phasis.dev (or in docs/ if you're reading the repo).

• Getting Started: install and run your first script
• CLI: bin/phasis and bin/test262
• API: full Phasis\Engine reference
• Parser: standalone Phasis\Parser\Parser API, AST walker, ESTree export
• Interop: PHP↔JS values, host functions, shared objects
• Compatibility: test262 coverage, spec surface, limitations
• Advanced: architecture, bytecode VM, oracle testing, benchmarks

License

MIT