为什么统计函数不行

Question

源码：

@header("content-Type: text/html; charset=utf-8");
$demon = 'www.php.cn';
$Chinese = 'PHP中文网';
echo strlen($demon),'

---

';
echo strlen($中文),'

---

';
echo mb_strlen($demon) ,'

---

';
echo mb_strlen($Chinese),'

---

';
echo mb_strwidth($demon),'

---

';
echo mb_strwidth($Chinese) ),'

---

';

输出：

10

12

10

12

10

12