php-pegjs v0.8.10

PHP PEG.js

This repo is not maintained for a while please use phpegjs module instead

PHP PEG.js is a php code generation plugin for PEG.js.

Requirements

• PEG.js

Installation

Node.js

Install PEG.js with php-pegjs plugin

$ npm install php-pegjs

Usage

Generating a Parser

In Node.js, require both the PEG.js parser generator and the php-pegjs plugin:

var pegjs = require("pegjs");
var phppegjs = require("php-pegjs");

To generate a php parser, pass to pegjs.buildParser php-pegjs plugin and your grammar:

var parser = pegjs.buildParser("start = ('a' / 'b')+", {
    plugins: [phppegjs]
});

The method will return source code of generated parser as a string. Unlike original PEG.js, generated php parser will be a class, not a function.

Supported options of pegjs.buildParser:

• cache — if true, makes the parser cache results, avoiding exponential parsing time in pathological cases but making the parser slower (default: false). In case of php, this is strongly recommended for big grammars (like javascript.pegjs or css.pegjs in example folder)
• allowedStartRules — rules the parser will be allowed to start parsing from (default: the first rule in the grammar)

Additional PHP PEG.js plugin options:

• phppegjs.parserNamespace - namespace of generated parser (default: "PhpPegJs"). If value is "", parser will be in global namespace
• phppegjs.parserClassName - name of generated class for parser (default: "Parser")

Using the Parser

1) Save parser generated by pegjs.buildParser to a file

2) In php code:

include "your.parser.file.php";

try
{
    $parser = new PhpPegJs\Parser;
    $result = $parser->parse($input);
}
catch (PhpPegJs\SyntaxError $ex)
{
    // Handle parsing error
    // [...]
}

You can use following snippet to format parsing error:

catch (PhpPegJs\SyntaxError $ex)
{
    $message = "Syntax error: " . $ex->getMessage() . ' At line ' . $ex->grammarLine . ' column ' . $ex->grammarColumn . ' offset ' . $ex->grammarOffset;
}

Grammar Syntax and Semantics

See documentation of PEG.js with one difference: action blocks should be written on PHP.

Original PEG.js rule:

media_list
  = head:medium tail:("," S* medium)* {
      var result = [head];
      for (var i = 0; i < tail.length; i++) {
        result.push(tail[i][2]);
      }
      return result;
    }
    

PHP PEG.js rule:

media_list
  = head:medium tail:("," S* medium)* {
      $result = array($head);
      for ($i = 0; $i < count($tail); $i++) {
        $result[] = $tail[$i][2];
      }
      return $result;
    }
    

You can also use following util functions in action blocks:

chr_unicode($code) - return character by its UTF-8 code (Analogue of javascript String.fromCharCode)

Guide of converting PEG.js action blocks to PHP PEG.js

Function $this->location() returns object with following structure:

{
  'start' => {
     'offset' => int,
     'line'   => int,
     'column' => int,
  },
  'end' => {
     'offset' => int,
     'line'   => int,
     'column' => int,
  },
}

License

The MIT License (MIT)