wordpress评论页面添加加减法验证，防止垃圾评论方法

//评论添加验证码
function spam_protection_math(){
$num1=rand(0,9);
$num2=rand(0,9);
echo "<label for="\&quot;math\&quot;">人机认证: <i>$num1 + $num2 = ?</i> </label>\n";
echo "<input class="\&quot;text\&quot;" tabindex="\&quot;4\&quot;" name="\&quot;sum\&quot;" size="\&quot;25\&quot;" type="\&quot;text\&quot;" value="\&quot;\&quot;" />\n";
echo "<input name="\&quot;num1\&quot;" type="\&quot;hidden\&quot;" value="\&quot;$num1\&quot;" />\n";
echo "<input name="\&quot;num2\&quot;" type="\&quot;hidden\&quot;" value="\&quot;$num2\&quot;" />";
}
function spam_protection_pre($commentdata){
$sum=$_POST['sum'];
switch($sum){
case $_POST['num1']+$_POST['num2']:
break;
case null:
wp_die('对不起: 请输入验证码。<a>返回上一页</a>','评论失败');
break;
default:
wp_die('对不起: 验证码错误，请<a>返回</a>重试。','评论失败');
}
return $commentdata;
}
if($comment_data['comment_type']==''){
add_filter('preprocess_comment','spam_protection_pre');
}

<?php spam_protection_math();?>