Rust PHP Parser

A fast, fault-tolerant PHP parser written in Rust. Produces a full typed AST with source spans, recovers from syntax errors, and covers PHP 7.4–8.5 syntax.

Try the interactive playground → · AST Node Reference →

Installation

[dependencies]
php-rs-parser = "*"
php-ast = "*"       # AST types and visitor/fold traits

# Optional
php-printer = "*"   # pretty-print AST back to PHP source
bumpalo = "*"       # only needed when using parse_arena() directly

Quick Start

use php_rs_parser::parse;

let result = parse("<?php echo 'Hello, world!';");

println!("{:#?}", result.program);

for err in &result.errors {
    println!("error at {:?}: {}", err.span(), err);
}

// Resolve byte offsets to line/column
let pos = result.source_map.offset_to_line_col(6);

parse returns a [ParseResult] with no lifetime parameters — the AST is fully owned and can be stored anywhere.

ParseResult fields

Field	Type	Description
program	php_ast::owned::Program	The parsed AST. Always present, even when errors exist.
errors	Vec<ParseError>	Parse errors and diagnostics. Empty on success.
errors_truncated	bool	true when the error list was capped.
source	String	The original source text. Slice spans: &result.source[span.start as usize..span.end as usize].
comments	Vec<php_ast::owned::Comment>	All comments in source order, not attached to AST nodes.
source_map	SourceMap	Pre-computed line index for offset_to_line_col.

Usage

Version-aware parsing

The parser targets PHP 8.5 by default. Use parse_versioned() to target an earlier version:

use php_rs_parser::{parse_versioned, PhpVersion};

let result = parse_versioned(
    "<?php enum Status { case Active; }",
    PhpVersion::Php80,
);
// Enums require PHP 8.1 — a VersionTooLow diagnostic is emitted.
assert!(!result.errors.is_empty());

Supported versions: Php74, Php80, Php81, Php82, Php83, Php84, Php85.

Error recovery

The parser never fails — it always produces a complete AST. Unrecoverable statements become StmtKind::Error nodes so the tree is structurally intact:

let result = php_rs_parser::parse("<?php function f() { $ }");
assert!(!result.errors.is_empty());
assert!(!result.program.stmts.is_empty());

Re-parsing (LSP / editor use)

ParserContext reuses the backing arena in O(1) across repeated parses. reparse_owned() returns a fully-owned ParseResult:

let mut ctx = php_rs_parser::ParserContext::new();
let a = ctx.reparse_owned("<?php echo 1;");
let b = ctx.reparse_owned("<?php echo 2;"); // a stays alive

reparse_versioned and reparse_owned_versioned are also available.

Visitor API

OwnedVisitor works directly on a ParseResult. Override only the node types you care about; the defaults recurse into children automatically:

use php_ast::owned::{OwnedVisitor, walk_owned_expr, Expr, ExprKind};
use std::ops::ControlFlow;

struct VarCounter { count: usize }

impl OwnedVisitor for VarCounter {
    fn visit_expr(&mut self, expr: &Expr) -> ControlFlow<()> {
        if matches!(&expr.kind, ExprKind::Variable(_)) {
            self.count += 1;
        }
        walk_owned_expr(self, expr)
    }
}

let result = php_rs_parser::parse("<?php $x = $y + $z;");
let mut v = VarCounter { count: 0 };
v.visit_program(&result.program);
assert_eq!(v.count, 3);

Return ControlFlow::Break(()) to stop early. Return ControlFlow::Continue(()) without calling walk_owned_* to skip a subtree.

Use OwnedScopeVisitor + OwnedScopeWalker when you need to know which namespace, class, or function you are currently inside — every visit method receives an OwnedScope. See docs.rs/php-ast for details.

AST transformation

FoldOwned rebuilds the AST, letting you transform specific nodes. Override only what you need; all other nodes are rebuilt identically:

use php_ast::owned::{FoldOwned, fold_owned_expr, Expr, ExprKind};

struct NegateInts;

impl FoldOwned for NegateInts {
    fn fold_expr(&mut self, expr: &Expr) -> Expr {
        if let ExprKind::Int(n) = &expr.kind {
            return Expr { kind: ExprKind::Int(-n), span: expr.span };
        }
        fold_owned_expr(self, expr)
    }
}

let result = php_rs_parser::parse("<?php $x = 1;");
let transformed = NegateInts.fold_program(&result.program);

Pretty printer

let result = php_rs_parser::parse("<?php echo 1 + 2;");
let output = php_printer::pretty_print_owned(&result.program);
// output == "<?php\necho 1 + 2;"

Use pretty_print_owned_file to append a trailing newline. Pass a PrinterConfig for custom indentation:

use php_printer::{PrinterConfig, Indent};

let config = PrinterConfig { indent: Indent::Spaces(2), ..Default::default() };
let output = php_printer::pretty_print_owned_with_config(&result.program, &config);

To preserve comments:

let output = php_printer::pretty_print_owned_with_comments(
    &result.program,
    &result.source,
    &result.comments,
);

PHPDoc parser

use php_rs_parser::phpdoc::{parse, find_tags, body_text};

let doc = parse("/** @param int $x The value\n * @return bool */");
for param in find_tags(&doc, "param") {
    println!("{}", body_text(&param.body).unwrap_or_default()); // "int $x The value"
}

Arena API

For maximum throughput or when you already hold an ArenaParseResult (e.g. inside an LSP hot path), use parse_arena() and the arena-form Visitor / Fold / pretty_print functions. See docs.rs/php-ast for the arena visitor and fold traits.

Architecture

Crate	crates.io	Purpose
php-lexer		Hand-written tokenizer with handling for strings, heredoc/nowdoc, and inline HTML
php-ast		AST type definitions; arena Visitor/ScopeVisitor/Fold traits; owned OwnedVisitor/OwnedScopeVisitor/FoldOwned traits
php-rs-parser		Pratt-based recursive descent parser with panic-mode error recovery, PHPDoc parser, source map
php-printer		Pretty printer — converts AST back to PHP source; supports both arena and owned AST

Source flows through Lexer → Parser → arena-allocated AST nodes. The lexer is lazy (tokens produced on demand with peeking slots); the parser is Pratt-based recursive descent with panic-mode error recovery. The owned AST (php_ast::owned) provides lifetime-free mirrors of every node type for storage and manipulation without arena lifetime constraints.

Performance

The fastest full-featured PHP parser. Optimised for modern PHP applications with full typing (PHP 7.4+, 8.x). For comparative benchmarks against other PHP parsers see php-parser-benchmark.

Contributing

See CONTRIBUTING.md for build instructions, testing, and contributor guides.

Acknowledgements

Inspired by and indebted to nikic/PHP-Parser — test corpus fixtures were adapted from its test suite. Thanks to the PHP community contributors.

License

BSD 3-Clause