class Demo
{
    private $name='張三';
    private $lei='類';
    private $abc='品牌';
    const TXET_WORD='文本字';

    public function __get($name)
    {
        if ($name == 'lei') {
            return $name.'不允許查看';
        }
        return $this->$name;
    }

    public function __set($name, $value)
    {
        if ($name == 'lei') {
            echo $name.'不允許修改;
        }
        $this->$name = $value;
    }

    public function __isset($name)
    {
        if ($name == 'lei') {
            return false;
        }
        return isset($this->$name);
    }

    public function __unset($name)
    {
        if ($name == 'name') {
            return false;
        }
        unset($this->$name);
    }
}
$demo=new Demo();

echo '姓名: ', $demo->name;

$demo->lei='你好';
$demo->name='hello';
echo Demo::TXET_WORD;
echo $demo->name;

echo isset($demo->name)?'存在':'不存在';
echo isset($demo->lei)?'存在':'不存在';

unset($demo->name);
echo $demo->name;