彻底解决WordPress博客垃圾评论的问题

<?php

/*
 Plugin Name: 简单算术题评论验证码插件
 Plugin URI:  http://www.utubon.com/wordpress-plugin-comment-capatcha-figure/
 Description: 提交评论之前必须写出简单的算术题答案
 Version: 1.0
 Author: 否子戈
 Author URI: http://www.utubon.com
*/

if(!class_exists('comment_capatcha')) {
    class comment_capatcha {
        function __construct() {
            add_action('comment_form', array(& $this, 'print_capatcha'));
            add_filter('preprocess_comment', array(& $this, 'preprocess_comment'));
        }
        function print_capatcha() {
            if(!is_user_logged_in()) {
                global $post;
                session_start();
                $rand_1 = mt_rand(1,6);
                $rand_2 = mt_rand(1,6);
                $_SESSION['capatcha_'.$post->ID] = $rand_1 + $rand_2;

                $str  = '<div id="capatcha-area"><label>';
                $str .= "{$rand_1} + {$rand_2} = ".'<input type="text" size="2" name="capatcha" id="capatcha" />';
                $str .= 'Result<span class="required">*</span>';
                $str .= '</label></div>';
                $str .= '<br>';
                echo $str; 
            }
        }
        function preprocess_comment($commentdata) {
            if(!is_user_logged_in()) {
                session_start();
                $post_id = isset($_POST['comment_post_ID']) ? $_POST['comment_post_ID'] : 0;
                if(!$post_id){
                    wp_die('数据来源非法。');
                }
                $capatcha = $_SESSION['capatcha_'.$post_id];
                if($capatcha != $_POST['capatcha']){
                    wp_die( __('请返回后重新输入算数题答案！') );
                }
                unset($_SESSION['capatcha_'.$post_id]);
            }
            return $commentdata;
        }
    }

}

if( !isset($comment_capatcha) ) {
    $comment_capatcha =& new comment_capatcha();
}

?>