WordPress注册用户页面添加验证码

//WordPress新用户注册随机数学验证码
 
function add_security_question_fields() {
//获取两个随机数, 范围0~9
   $num1=rand(0,9);
   $num2=rand(0,9);
//最终网页中的具体内容
   echo "<p><label for='math' class='small'>验证码：$num1 + $num2 = ? </label><input type='text' name='sum' class='input' value='' size=
'25'>"    ."<input type='hidden' name='num1' value='$num1'>"
    ."<input type='hidden' name='num2' value='$num2'></p>";}
    add_action('register_form','add_security_question_fields');
    add_action( 'register_post', 'add_security_question_validate', 10, 3 );
    function add_security_question_validate( $sanitized_user_login, $user_email, $errors) {
    $sum=$_POST['sum'];//用户提交的计算结果
    switch($sum){
//得到正确的计算结果则直接跳出
    case $_POST['num1']+$_POST['num2']:break;
//未填写结果时的错误讯息
    case null:wp_die('错误：请输入验证码！');break;
//计算错误时的错误讯息
    default:wp_die('错误：验证码错误,请重试！');}}
add_action( 'add_security_question','register_form' );