PPC

A parser combinator library for PHP

Simple to use & extend • Fast & lightweight • Reliable

Introduction

PPC stands for PHP Parser Combinator. What an obvious name for such a library!

As its name tells us, PPC is just another parser combinator library with a clear goal: make writing efficient parsers a breeze. Writing parser with PPC does not require you to know how parser combinators works internally nor it requires you to learn a complex object-oriented API.

PPC is a set of functions which you will love to compose to build complex parsers! Parsers are plain closures: they never copy the input, and backtracking costs nothing.

Installation

PPC requires PHP 8.5 and the Multibyte String (mbstring) extension.

composer require "jubianchi/ppc" "dev-master"

Example parser

Here is a quick example demonstrating how easy it is to write a parser:

<?php

use jubianchi\PPC\SyntaxError;

use function jubianchi\PPC\{char, enclosed, eos, map, optional, parse, regex, separated, seq, terminated};

$digit = regex('/[0-9]/') |> map(intval(...));
$separator = seq(char(','), char(' ') |> optional());
$list = terminated(enclosed(char('['), separated($separator, $digit), char(']')), eos());

assert(parse($list, '[0, 1, 2]') === [0, 1, 2]);

try {
    parse($list, '[0, 1 2]');
} catch (SyntaxError $error) {
    assert($error->getMessage() === 'Expected "," or "]", got " " at line 1, column 6');
}

Easy, right? Be sure to read the documentation to understand how it works.

Concepts

PPC has four kinds of functions, each with a single job:

Kind	Job	Examples
Parsers	read the input	char(), word(), regex(), eos()
Combinators	assemble parsers into a new parser, without reading the input themselves	seq(), alt(), many(), separated()
Modifiers	transform the result of a parser, without reading more input; always applied with the pipe operator	|> map(), |> label()
Runners	run a parser on an input and give back its value, or the syntax error	parse(), stream(), tryParse(), tryStream()

Any combination of parsers, combinators and modifiers is a parser, which can be combined again. And reading a definition tells what it does: functions taking parsers build the grammar, and the pipe operator never reads more input.

See CONTRIBUTING.md for the detailed rules.