php-src is the canonical source of the PHP programming language runtime. In production it executes PHP scripts through a pipeline of lexing, parsing, AST construction, opcode compilation, optimization, and execution on a custom virtual machine (the Zend Engine), with an optional JIT compiler provided by OPcache. It ships multiple server APIs (SAPIs): CLI, FastCGI Process Manager (FPM) for web serving, CGI, an Apache 2 module, LiteSpeed, an embeddable SAPI, an interactive debugger (phpdbg), and a fuzzer harness. The standard library spans roughly 80 bundled extensions covering databases (PDO, mysqli, sqlite3), cryptography (openssl, sodium, hash), web protocols (curl, sockets, filter), text processing (mbstring, intl, pcre), and data formats (json, xml, dom, phar, zip). The architecture is a modular C codebase. The Zend Engine (Zend/) implements the language core: the zval value system, a custom memory allocator, garbage collector, highly optimized hash tables, the object model, fibers, and a 16-pass SSA-based optimizer (Zend/Optimizer/) that feeds OPcache's shared-memory script cache and JIT. Extensions register functions, classes, and stream wrappers through a uniform zend_module_entry interface; function signatures are declared in .stub.php files and compiled into generated arginfo headers. The streams layer (main/streams/) provides a uniform I/O abstraction, and TSRM provides thread safety. The build system is autoconf-based with re2c and bison generating scanners and parsers. Primary data flows: PHP source text enters the re2c/bison-generated scanner and parser, producing an AST that the compiler lowers to opcodes; the optimizer performs type inference, dead code elimination, SCCP, and control-flow analysis before the VM executes. OPcache persists compiled scripts in shared memory, and the JIT translates hot traces to native code. Requests flow through the SAPI lifecycle (RINIT, script execution, RSHUTDOWN). Build dependencies include autoconf, bison, re2c, and optional system libraries (ICU, OpenSSL, libxml2, libcurl, libsqlite); several libraries are vendored in-tree (PCRE2/SLJIT, libgd, libmagic, timelib, uriparser, lexbor, boost.context, Keccak). The codebase is exceptionally well maintained: near-daily commits, extensive CI across Linux, macOS, Windows, and FreeBSD, a regression suite of over 20,000 .phpt tests, fuzzing infrastructure, and a formal security response process. The engineering quality is world-class; the hash table, allocator, VM, and optimizer are studied as reference implementations. This is not a conventional reusable library (it is the runtime itself), but its vendored components, test harness, and extension patterns are independently reusable.
This repository is a production-grade Rust implementation of the Starlark language, the deterministic Python-like configuration language used by build systems such as Bazel and Buck2. The system is structured as a multi-crate workspace: `starlark` provides the core runtime (parser, bytecode compiler, evaluator, garbage-collected heap, type system, and standard library), `starlark_syntax` handles parsing and AST, `starlark_map` offers high-performance ordered hash maps and sets, `starlark_derive` supplies procedural macros for defining Starlark-compatible Rust types, and `starlark_bin` bundles a CLI with REPL, linter, and Debug Adapter Protocol (DAP) server. Additional crates include `starlark_lsp` for Language Server Protocol support and a WASM example for embedding in JavaScript. The architecture is a classic interpreter pipeline: source text is parsed into an AST (`AstModule`), compiled to bytecode (with optimizations like constant folding, speculative execution, and inlining), and executed by a stack-based bytecode VM. Values are managed on a two-tier heap (unfrozen mutable and frozen immutable) with a custom bump allocator and explicit freeze operations. The type system supports both runtime type checking and static analysis, including union types, callable signatures, and generic type matchers. External dependencies include the `tower-lsp` and `lsp-types` crates for the LSP server, and several internal Facebook crates (e.g., `buck2_core`, `buck2_data`) for pagable serialization and profiling. Key entry points are `starlark::eval::eval_module` for programmatic evaluation, `starlark_bin/bin/main.rs` for the CLI, and the `#[starlark_module]` and `#[starlark_value]` proc macros for extending the language with custom types and functions. The system is designed for embedding in build tools, with a focus on performance, determinism, and debuggability.