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

Javascript code	PHP analogue
some_var	$some_var
{f1: "val1", f2: "val2"}	array("f1" => "val1", "f2" => "val2")
["val1", "val2"]	array("val1", "val2")
some_array.push("val")	$some_array[] = "val"
some_array.length	count($some_array)
some_array.join("")	join("", $some_array)
some_array1.concat(some_array2)	array_merge($some_array1, $some_array2)
parseInt("23")	intval("23")
parseFloat("23.1")	floatval("23.1")
some_str.length	mb_strlen(some_str, "UTF-8")
some_str.replace("b", "\b")	str_replace("b", "\b", $some_str)
String.fromCharCode(2323)	chr_unicode(2323)
text()	$this->text()
location()	$this->location()

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)