diff --git includes/common.inc includes/common.inc
index a70d26e..272d939 100644
--- includes/common.inc
+++ includes/common.inc
@@ -4469,14 +4469,94 @@ function drupal_clear_js_cache() {
 /**
  * Converts a PHP variable into its Javascript equivalent.
  *
- * We use HTML-safe strings, i.e. with <, > and & escaped.
+ * We use HTML-safe strings, with several characters escaped.
  *
  * @see drupal_json_decode()
- * @ingroup php_wrappers
  */
 function drupal_json_encode($var) {
-  // json_encode() does not escape <, > and &, so we do it with str_replace().
-  return str_replace(array('<', '>', '&'), array('\u003c', '\u003e', '\u0026'), json_encode($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.
+      $replace_pairs = array(
+        // ", \ and U+0000 - U+001F must be escaped according to RFC 4627.
+        '\\' => '\u005c',
+        '"' => '\u0022',
+        "\x00" => '\u0000',
+        "\x01" => '\u0001',
+        "\x02" => '\u0002',
+        "\x03" => '\u0003',
+        "\x04" => '\u0004',
+        "\x05" => '\u0005',
+        "\x06" => '\u0006',
+        "\x07" => '\u0007',
+        "\x08" => '\u0008',
+        "\x09" => '\u0009',
+        "\x0a" => '\u000a',
+        "\x0b" => '\u000b',
+        "\x0c" => '\u000c',
+        "\x0d" => '\u000d',
+        "\x0e" => '\u000e',
+        "\x0f" => '\u000f',
+        "\x10" => '\u0010',
+        "\x11" => '\u0011',
+        "\x12" => '\u0012',
+        "\x13" => '\u0013',
+        "\x14" => '\u0014',
+        "\x15" => '\u0015',
+        "\x16" => '\u0016',
+        "\x17" => '\u0017',
+        "\x18" => '\u0018',
+        "\x19" => '\u0019',
+        "\x1a" => '\u001a',
+        "\x1b" => '\u001b',
+        "\x1c" => '\u001c',
+        "\x1d" => '\u001d',
+        "\x1e" => '\u001e',
+        "\x1f" => '\u001f',
+        // Prevent browsers from interpreting these as as special.
+        "'" => '\u0027',
+        '<' => '\u003c',
+        '>' => '\u003e',
+        '&' => '\u0026',
+        // Prevent browsers from interpreting the solidus as special and
+        // non-compliant JSON parsers from interpreting // as a comment.
+        '/' => '\u002f',
+        // While these are allowed unescaped according to ECMA-262, section
+        // 15.12.2, they cause problems in some JSON parser.
+        "\xe2\x80\xa8" => '\u2028', // U+2028, Line Separator.
+        "\xe2\x80\xa9" => '\u2029', // U+2029, Paragraph Separator.
+      );
+
+      return '"'. strtr($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) {
+          $output[] = drupal_json_encode($v);
+        }
+        return '[ '. implode(', ', $output) .' ]';
+      }
+      // Otherwise, fall through to convert the array as an object.
+    case 'object':
+      $output = array();
+      foreach ($var as $k => $v) {
+        $output[] = drupal_json_encode(strval($k)) .': '. drupal_json_encode($v);
+      }
+      return '{ '. implode(', ', $output) .' }';
+    default:
+      return 'null';
+  }
 }
 
 /**