src/Sparkline.php
public function getServerValue($key)
    {
        if (isset($this->server[$key])) {
            return $this->server[$key];
        }

        return null;
    }
public function getServerValue($key)
    {
        if (isset($this->server[$key])) {
            return $this->server[$key];
        }

        return null;
    }
@param $key

@return mixed|null