Possible fix for #5470: (#5506)

Possible fix for #5470: (#5506)

- $data is not an object like stdClass but an array
- newer PHP versions doesn't allow cross-access like following:

  $object['foo'] = 123;
  $array->foo = 123;

- added type-hints for private methods for above cases
- used `if (empty($foo)) instead of just `if ($foo)` preventing some nasty
  E_NOTICE
- added some empty lines for better readability