<?php

/**

 * @file

 * Provides a helper to properly encode HTML-safe JSON prior to PHP 5.3.0.

 */

/**

 * Encodes a PHP variable to HTML-safe JSON for PHP versions below 5.3.0.

 *

 * @see drupal_json_encode()

 */

function drupal_json_encode_helper($var) {

  switch (gettype($var)) {

    case 'boolean':

      return $var ? 'true' : 'false'; // Lowercase necessary!

    case 'integer':

    case 'double':

      return $var;

    case 'resource':

    case 'string':

      // Always use Unicode escape sequences (\u0022) over JSON escape

      // sequences (\") to prevent browsers interpreting these as

      // special characters.

      $replace_pairs = array(

        // ", \ and U+0000 - U+001F must be escaped according to RFC 4627.

        '\\' => '\u005C',

        '"' => '\u0022',

        "\x00" => '\u0000',

        "\x01" => '\u0001',

        "\x02" => '\u0002',

        "\x03" => '\u0003',

        "\x04" => '\u0004',

        "\x05" => '\u0005',

        "\x06" => '\u0006',

        "\x07" => '\u0007',

        "\x08" => '\u0008',

        "\x09" => '\u0009',

        "\x0a" => '\u000A',

        "\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.

        "'" => '\u0027',

        '<' => '\u003C',

        '>' => '\u003E',

        '&' => '\u0026',

        // Prevent browsers from interpreting the solidus as special and

        // non-compliant JSON parsers from interpreting // as a comment.

        '/' => '\u002F',

        // While these are allowed unescaped according to ECMA-262, section

        // 15.12.2, they cause problems in some JSON parsers.

        "\xe2\x80\xa8" => '\u2028', // U+2028, Line Separator.

        "\xe2\x80\xa9" => '\u2029', // U+2029, Paragraph Separator.

      );

      return '"' . strtr($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) {

          $output[] = drupal_json_encode_helper($v);

        }

        return '[ ' . implode(', ', $output) . ' ]';

      }

      // Otherwise, fall through to convert the array as an object.

    case 'object':

      $output = array();

      foreach ($var as $k => $v) {

        $output[] = drupal_json_encode_helper(strval($k)) . ':' . drupal_json_encode_helper($v);

      }

      return '{' . implode(', ', $output) . '}';

    default:

      return 'null';

  }

}