According to the documentation on [PHP Array Operators](http://www.php.net/manual/en/language.operators.array.php):

> The + operator returns the right-hand array appended to the left-hand array; for keys that exist in both arrays, the elements from the left-hand array will be used, and the matching elements from the right-hand array will be ignored.

So this should be:

    $this->options = $options + $this->options;

I hope this helps!