下面是一个最简单的工作示例。。。（注意：这是未测试的代码。）

add_action(\'init\', \'custom_rsvp_handler\');
function custom_rsvp_handler() {
    // for singular posts only
    // (could also check for event post type here)
    if (!is_singular()) {return;}

    // set cookie expiry length (eg. 28 days)
    $cookielength = time()+(60*60*24*28);

    // set a cookie key based on post ID
    global $post; $cookiekey = \'rsvp-\'.$post->ID;

    // set global to access RSVP state in shortcode
    global $rsvp;

    // check if already visited (RSVP cookie set)
    if (isset($_COOKIE[$cookiekey])) {$rsvp = $_COOKIE[$cookiekey];}

    // check for RSVP querystring (clicked email link with ?rsvp=1)
    // (or clicked attending after clicking not attending)
    if (isset($_GET[\'rsvp\'])) {
        $ip = $_SERVER[\'REMOTE_ADDR\'];
        // check for email click
        if ($_GET[\'rsvp\'] == \'1\') {
            $rsvp = \'1\'; 
            if (!isset($_COOKIE[$cookiekey])) {
                // assume this is a new click and set cookie
                setcookie($cookiekey, \'1\', $cookielength);
                // record the IP to the post meta
                $ips = get_post_meta($post->ID, \'rsvps\');
                if ( (!is_array($ips)) || (!in_array($ip, $ips)) ) { 
                    $ips[] = $ip; update_post_meta($post->ID, \'rsvps\', $ips);
                    update_post_meta($post->ID, \'rsvp-count\', count($ips));
                }
            }
        } elseif ($_GET[\'rsvp\'] == \'0\') {
            // user clicked not attending button
            $rsvp = \'0\'; setcookie($cookiekey, \'0\', $cookielength);
            // remove IP from attending list
            $ips = get_post_meta($post->ID, \'rsvps\');
            if ( (is_array($ips)) || (in_array($ip, $ips)) ) { 
                    $index = array_search($ip, $ips); unset($ips[$index]);
                    update_post_meta($post->ID, \'rsvps\', $ips);
                    update_post_meta($post->ID, \'rsvp-count\', count($ips));
                }
            }
        }
    }
}

// shortcode for a non-attending button
add_shortcode(\'rsvp-button\', \'custom_rsvp_button\');
function custom_rsvp_button() {
    global $rsvp;
    if (!isset($rsvp)) {return \'\';}
    if ($rsvp == \'1\') {$action = \'I Cannot Attend\'; $switch = \'0\';}
    if ($rsvp == \'0\') {$action = \'I Can Attend\'; $switch = \'1\';}
    $button = \'<form method="get" action="\'.$_SERVER[\'PHP_SELF\'].\'">\';
    $button .= \'<input type="hidden" name="rsvp" value="\'.$switch.\'">\';
    $button .= \'<input type="submit" value="\'.$action.\'">\';
    $button .= \'</form>\';
    return $button;
}

add_shortcode(\'rsvp-count\', \'custom_rsvp_count\');
function custom_rsvp_count() {
    global $rsvp, $post;
    if (!isset($rsvp)) {return;}
    $attendees = get_post_meta($post->ID, \'rsvp-count\');
    if ($attendees) {return $attendees." Attending";}
    return \'\';
}

这将把IP列表保存到事件帖子的meta中，并为访问者设置一个cookie作为参与者，这将（大致）防止重复记录。

然后，您可以将快捷码[rvsp按钮]添加到活动帖子内容中，以便页面访问者可以在访问页面后单击“我无法参加”。或“我可以参加”，如果他们已经点击他们不能参加。（未通过电子邮件链接到达的访问者将看不到该按钮。）

更新：为输出rsvp参与计数添加了post meta和shortcode[rsvp计数]。