class font
{
    private static  $veri = null;

    public static function yazi($yazi)
    {
        self::$veri = $yazi;
        return new static;
    }
    public static function bold_yap()
    {
        self::$veri = '<strong>'.self::$veri.'</strong>';
        return new static;
    }
    public static function veriyi_al()
    {
        return self::$veri;
    }
}
echo font::yazi('test')->bold_yap()->veriyi_al();