Phargo

A from-scratch, memory-safe PHP engine written in Rust — built the same way the Bun team rewrote Bun in Rust: drive an AI with the original project's own test suite as the oracle, and watch the pass-rate climb in public.

North star: run WordPress in the browser

WordPress Playground runs WordPress entirely in your browser by compiling the C PHP interpreter to WebAssembly via Emscripten. Those WASM builds are big, and the Playground team has been actively fighting binary size. Rust → WASM is leaner and memory-safe by construction. So the goal:

A PHP engine in Rust that passes PHP's own .phpt tests and boots WordPress inside Playground — at a fraction of the WASM size.

Honesty

I'm not (yet) a Rust or PHP-internals expert. This is an open experiment in AI-assisted engineering. The wins and the failures are in the open, and the scoreboard never lies — see PROGRESS.md.

How it works

• src/lang/ — the engine: a proper language implementation — byte-level lexer (lexer.rs/token.rs) → recursive-descent parser → owned AST (ast.rs/parser.rs) → tree-walking evaluator (value.rs/eval.rs). run(php_source) -> printed output.
• src/lib.rs — a 52-line crate root: the public run/run_with_path entry points + the shared subsystems the evaluator reuses (regex.rs, datetime.rs).
• src/main.rs — the scoreboard. Runs every .phpt in vendor/php-src/, compares output to each test's expected section, writes PROGRESS.md.
• tests/phpt/ — curated smoke tests. Real PHP .phpt format: each file bundles the code and its expected output, so we can score against it with no PHP runtime installed.

Note: the engine was rebuilt from scratch (the original single-pass interpreter is retired). The from-scratch lexer→parser→AST→evaluator now passes more corpus tests than the engine it replaced — see the git history.

Run it

cargo run

Status

v2 engine: 3645 / 22037 upstream php-src tests passing (16.5% of gradeable). Rebuilt from scratch as a real lexer→parser→AST→evaluator, the engine passes far more corpus tests than the original single-pass interpreter it replaced (1,981), with byte-correct strings (Vec<u8>), correct operator precedence, and an AST (parse once, no re-parsing). The core language is there — variables + real references (&$x/=&/use(&$x)), the full operator/type-juggling model, control flow, generators (yield), functions/closures (variadics, argument unpacking, named args, Closure::bind/bindTo/fromCallable), arrays + ~300 builtins, classes/interfaces/traits/enums (+ typed constants, asymmetric visibility, method-visibility enforcement), exceptions, attributes, the 8.5 pipe operator |>, dynamic dispatch, Reflection, the SPL iterator/container family, ArrayAccess, superglobals + sessions, date/time (DateTime/strtotime), a from-scratch regex engine (preg_*), a from-scratch XML parser powering DOMDocument + SimpleXML, file streams (fopen), include/require/eval, serialize/unserialize (+ __serialize), and PHP-faithful var_dump/var_export. The remaining failures are overwhelmingly out-of-scope C extensions (GD, SOAP, curl, PDO/mysqli, intl, FFI, Fiber…). The climb continues — see PROGRESS.md.