Using the php target

grammar Id;

options{
    language = Php;
}
ids: (id=Id{echo $id.text."\n";})+;

Id: Letter (Letter | '0'..'9' |'_')*;

fragment
Letter: 'A'..'Z'|'a'..'z';

Ws: ('\n' |'\r'|'\t'|' ')+ {$channel=self::\$HIDDEN;};

To generate the php files add the anltr jars to the CLASSPATH and run

java org.antlr.Tool Id.g

This will generate two Php files IdLexer.php and IdParser.php. You can build a program that uses the new parser.

<?php
require 'antlr/antlr.php'; //Path to the antlr runtime files
require 'IdLexer.php';
require 'IdParser.php';

function parser($expr){
        $ass = new ANTLRStringStream($expr);
        $lex = new IdLexer($ass);
        $cts = new CommonTokenStream($lex);
        $par = new IdParser($cts);
        return $par;
}

$par = parser("hello world");
$par->ids();
?>

Prints:

hello
world

What to watch out for

Parameters and return values for rules

Rule paramater declarations are prefixed with a dollar as in Php

rule [$param]

Return value declarations do not have the dollar symbol

rule returns [returned]

Php variable names

Antlr uses the $ symbol to indicate special variables. Due to this the $ symbol in the php code needs to be escaped.

\$total = \$total+(int)$num.text;