// Pattern :
// array(
//  [UTF8 (hex)] => [C/C++/Java Source code]
// );
// [updated] 10.06.2012

      $replace_pairs = array(
        // ", \ and U+0000 - U+001F must be escaped according to RFC 4627.
        "\x5c" => '\u005c',
        "\x22" => '\u0022',
        "\x00" => '\u0000',
        "\x01" => '\u0001',
        "\x02" => '\u0002',
        "\x03" => '\u0003',
        "\x04" => '\u0004',
        "\x05" => '\u0005',
        "\x06" => '\u0006',
        "\x07" => '\u0007',
        "\x08" => '\u0008',
        "\x09" => '\u0009', //TAB
        "\x0a" => '\u000a', //LF : Line Feed
        "\x0b" => '\u000b',
        "\x0c" => '\u000c',
        "\x0d" => '\u000d',
        "\x0e" => '\u000e',
        "\x0f" => '\u000f',
        "\x10" => '\u0010',
        "\x11" => '\u0011',
        "\x12" => '\u0012',
        "\x13" => '\u0013',
        "\x14" => '\u0014',
        "\x15" => '\u0015',
        "\x16" => '\u0016',
        "\x17" => '\u0017',
        "\x18" => '\u0018',
        "\x19" => '\u0019',
        "\x1a" => '\u001a',
        "\x1b" => '\u001b',
        "\x1c" => '\u001c',
        "\x1d" => '\u001d',
        "\x1e" => '\u001e',
        "\x1f" => '\u001f',
       
        // Prevent browsers from interpreting these as as special.
       
        "\x27" => '\u0027',
        "\x3c" => '\u003c',
        "\x3e" => '\u003e',

        "\x26" => '\u0026',
        "\x24" => '\u0024',
        "\x40" => '\u0040',

        "\x21" => '\u0021',
        "\x3a" => '\u003a',
        "\x3b" => '\u003b',
        "\x3f" => '\u003f',

        "\x5e" => '\u005e',

        "\x28" => '\u0028',
        "\x29" => '\u0029',

        "\x7c" => '\u007c',
        "\x60" => '\u0060',
        "\x7e" => '\u007e',

        // Prevent browsers from interpreting the solidus as special and
        // non-compliant JSON parsers from interpreting // as a comment.
       
        "\x2f" => '\u002f', // slash

        // While these are allowed unescaped according to ECMA-262, section
        // 15.12.2, they cause problems in some JSON parser.
        "\xe2\x80\xa8" => '\u2028', // U+2028, Line Separator.
        "\xe2\x80\xa9" => '\u2029', // U+2029, Paragraph Separator.
      );

      //return '"'. strtr($var, $replace_pairs) .'"';

      return '"' . unicode_replacer ( $var, $replace_pairs ) . '"';
     
    case 'array':
      // Arrays in JSON can't be associative. If the array is empty or if it
      // has sequential whole number keys starting with 0, it's not associative
      // so we can go ahead and convert it as an array.
      if (empty ($var) || array_keys($var) === range(0, sizeof($var) - 1)) {
        $output = array();
        foreach ($var as $v) {
          $output[] = drupal_to_js($v);
        }
        return '[ '. implode(', ', $output) .' ]';
      }
      // Otherwise, fall through to convert the array as an object.
    case 'object':
      $output = array();
      foreach ($var as $k => $v) {
        $output[] = drupal_to_js(strval($k)) .': '. drupal_to_js($v);
      }
      return '{ '. implode(', ', $output) .' }';
    default:
      return 'null';
  }
}

/*
 Alternate for strtr( ) looks like more speedy
*/

function unicode_replacer ( $text, $replace ) {
    $keys = array_keys($replace);
    $length = array_combine($keys, array_map('strlen', $keys));
    arsort($length);
   
    $array[] = $text;
    $count = 1;
    reset($length);
    while ($key = key($length)) {
        if (strpos($text, $key) !== false) {
            for ($i = 0; $i < $count; $i += 2) {
                if (($pos = strpos($array[$i], $key)) === false) continue;
                array_splice($array, $i, 1, array(substr($array[$i], 0, $pos), $replace[$key], substr($array[$i], $pos + strlen($key))));
                $count += 2;
            }
        }
        next($length);
    }
    return implode( $array );
}

/**
 * Return data in JSON format.
 *
 * This function should be used for JavaScript callback functions returning
 * data in JSON format. It sets the header for JavaScript output.
 *
 * param $var
 *   (optional) If set, the variable will be converted to JSON and output.
 */
function drupal_json($var = NULL) {
  // We are returning JavaScript, so tell the browser.
 
    drupal_set_header('Content-Type: application/json; charset=utf-8');
 
  if (isset($var)) {
    echo drupal_to_js($var);
  }
}