我无法使用ajax和表单使这个插入db函数正常工作。当我执行此操作时，我会收到一个关于成功的空白警报框。

HTML

<div id="rsvpContent">  
     <form id="Attendevent" action="">
     <input id="attend" name="attend" type="checkbox" value="yes" /><label for="attent">Yes, I plan to attend.</label>
     <input type="hidden" value="<?php echo get_the_ID(); ?>" name="event_id"/>
     <input type="hidden" value="<?php echo $current_user->ID; ?>" name="user_id"/>
     </form>
</div>

 add_action(\'wp_ajax_Attending\', \'eventAttend\');
 add_action(\'wp_ajax_nopriv_Attending\', \'eventAttend\');

 function eventAttend() {
  global $wpdb;

  $fields = array();
  parse_str($_POST[\'data\'], $fields);

if($fields[\'attend\'] == \'yes\') {

   $wpdb->insert(\'wp_event_attendants\', array( \'event_id\' => $fields[\'event_id\'], \'user_id\' => $fields[\'user_id\'])); 

    echo $wpdb->print_error();
    }
    echo \'Not working.\';
   die();
}

    $("#attend").click(function(){
    var form = $("#Attendevent").serialize();

    $.ajax({
      url: "<?php echo admin_url(\'admin-ajax.php\'); ?>",
      beforeSend: function() {
          alert(form);
      },
      type:\'POST\',
      data:{
          action: "Attending",
          "data": form 
          },
      dataType:  \'html\',
      success: function(data) {
            alert(data);
      }
    }); 
});

【2013年3月7日17:47:09】PHP通知：未定义索引：参加/wp内容/插件/活动日历注册/功能。php在线198