Rework of BrowserInformation class using class variables correctly

BrowserInformation

class BrowserInformation
{
    private $agent;
    private $browser;
    
    public function __construct($agent = NULL)
    {
        if (empty($agent))
        {
            $agent = $_SERVER['HTTP_USER_AGENT'];
        }

        $this->agent = $agent;
        $this->browser = get_browser($agent, true);
    }
    
    public function platform()
    {
        $platform = $this->browser['platform'];

        //unknown check
        if ($platform === "unknown")
        {
            echo "IDK what OS you'r running<br />";
        }
        else
        {
            echo "You are on {$platform}<br />";
        }
    }
}


$client = new BrowserInformation();
$client->platform();