public function setRequestHeader($name, $value)
    {
        if (!is_string($name))
            throw new \InvalidArgumentException('Argument 1 expected to be string, '.gettype($name).' seen.');

        if (!is_string($value))
            throw new \InvalidArgumentException('Argument 2 expected to be string, '.gettype($value).' seen.');

        if (($name = trim($name)) === '')
            throw new \RuntimeException('Argument 1 cannot be empty string.');

        $this->requestHeaders[$name] = $value;

        return $this;
    }