There appears to be an oddity with json_encode and/or json_decode when attempting decode a string that was produced by json_encode:
$object = new stdClas
Thats because PHP is converting the double slashes into a single slash before passing it to json_decode. You will need to either escape the double slashes (a pain I know) or construct the object manually.
http://php.net/manual/en/language.types.string.php#language.types.string.syntax.single