<?
$pwd='123456';
if($_post['pwd'] == "$pwd")
{
echo '密码正确';
}
elseif($_post['submit'])
{
echo '请不要非法闯入';
}else{
echo '<form action="ad.php" method="POST">密码:<input type="text" name="pwd"><br>
<input type="submit" name="submit" value="提交"></from>';
}
?>