code: public function getServerParam(
          string $name,
          int $filter = \FILTER_DEFAULT,
          $options = null
      ) {
          // Can be useful if FastCGI has strange side-effects with unexpected null
          // values when using INPUT_SERVER and INPUT_ENV with this function.
          //return isset($_SERVER[$name]) ? filter_var($_SERVER[$name], $filter, $options)
          //    : null;
          return filter_input(\INPUT_SERVER, $name, $filter, $options);
      }
docs: The method returns the server parameter value by the key. It's wrapper over
  the filter_input() function.
  @param string $name Name of a variable to get.
  @param int $filter
  @param mixed $options Associative array of options or bitwise disjunction
  of flags. If filter accepts options, flags can be provided in "flags"
  field of array.
  @return mixed Value of the requested variable on success, false if the filter
  fails, or null if the variable is not set.