Replace filter_input in plugin construct

According to numerous reports filter_input(INPUT_SERVER…) on PHP with CGI/FastCGI might result in NULL being returned.
This happened to me recently and as such plugin’s constructor was assigning

$this->domain = $this->originalDomain;

which results in home page always redirecting to original domain.

Could you please fix it and use normal $_SERVER variables to determine domain instead of filter_input function?

Read comment from “anthony dot parsons at manx dot net” here for some details: https://php.net/manual/en/function.filter-input.php or google for ‘filter_input INPUT_SERVER returns null’ for bug confirmation.