Description:
------------
This prints not only line number but also specified string text when an error occurs in interpreting javascript code. Specify a prefer string to the second argument of evaluateScript() function call. It will help your debug javascript code in PHP. Of course it can be omitted.

The patch is spidermonkey-line-number.patch on http://developer.cybozu.co.jp/oss/2010/01/spidermonkey-ph.html

Reproduce code:
---------------
<?php
$js = new JSContext();
$js->registerFunction('var_dump');
$script = <<< END
    try {
        throw new Error('test message');
    } catch (e) {
        var_dump(e);
    }
END;

$js->evaluateScript($script, 'test call');

Expected result:
----------------
object(stdClass)#2 (4) {
  ["message"]=>
  string(12) "test message"
  ["fileName"]=>
  string(9) "test call"
  ["lineNumber"]=>
  int(1)
  ["stack"]=>
  string(38) "Error("test message")@:0
@test call:1
"