为什么我自己测试xss注入不成功呢？不是把js代码通过表单...

<form action="test.php" method="post">
<textarea name="post"><script>alert('看看弹出不');</script></textarea>
<input type="submit"> 
</form> 
<?php
header('Content-Type:text/html;charset=utf-8');
echo $_POST['post'];