protected function check($env_var, $functionName)
    {
        if ($value = fp_env($env_var, null)) {
            if ($this->$functionName()) {
                return $value;
            }
            $this->error("Be careful! The $env_var you provided doesn't match Laravel Forge server");
            return "<error>$value</error>";
        } else {
            return 'Not available!';
        }
    }