jquery.validate使用

<link href="/css/main.css" rel="stylesheet" type="text/css" />

<script type="text/javascript" src="/js/jquery-1.7.1.min.js"></script>   
<script type="text/javascript" src="/js/jquery.validate.min.js"></script>

<script type="text/javascript">
$(document).ready(function() {    
    $("#regforms").validate({
        rules: {
            username: {
                required: true,
                minlength: 2,
                remote: {   
                      url: "/do.php?ac=ajax&op=checkusername",     //后台处理程序   
                      type: "post",               //数据发送方式   
                      dataType: "json",           //接受数据格式      
                      data: {                     //要传递的数据，默认已传递应用此规则的表单项   
                          username: function() {   
                              return $("#username").val();   
                          }   
                      }  
                }

            },
            mobile:{required: true,
                rangelength: [11,11],
                telphoneValid:true,
                digits:true,
                remote: {   
                      url: "/do.php?ac=ajax&op=checkmobile",     //后台处理程序   
                      type: "post",               //数据发送方式   
                      dataType: "json",           //接受数据格式      
                      data: {                     //要传递的数据，默认已传递应用此规则的表单项   
                          mobile: function() {   
                              return $("#mobile").val();   
                          }   
                      }  
                }
            },
            password: {
                required: true,
                minlength: 5
            },
            confirm_password: {
                required: true,
                minlength: 5,
                equalTo: "#password"
            },
            email: {
                required: true,
                email: true,
                remote: {   
                      url: "/do.php?ac=ajax&op=checkemail",     //后台处理程序   
                      type: "post",               //数据发送方式   
                      dataType: "json",           //接受数据格式      
                      data: {                     //要传递的数据，默认已传递应用此规则的表单项   
                             email: function() {   
                              return $("#email").val();   
                          }   
                      }  
                }
            },question:{required: true}
            ,answer:{required: true}
        },
        messages: {
            username: {
                required: "Please enter a username",
                minlength: "Your username must consist of at least 2 characters",
                remote:"该用户名存在"
            },
            password: {
                required: "Please provide a password",
                minlength: "Your password must be at least 5 characters long"
            },
            confirm_password: {
                required: "Please provide a password",
                minlength:"Your password must be at least 5 characters long",
                equalTo: "Please enter the same password as above"
            },
            mobile:  {
                required: "<span style='color:#FF0000'>&nbsp;&nbsp;移动电话不能为空</span>",
                digits: "<span style='color:#FF0000'>&nbsp;&nbsp;移动电话号码必须是数字</span>"
                },
            email: "Please enter a valid email address"
        }
    });
});
//新增加 手机验证拓展
jQuery.validator.addMethod("telphoneValid", function(value, element) {
var tel = /^(130|131|132|133|134|135|136|137|138|139|150|153|157|158|159|180|187|188|189)\d{8}$/;
return tel.test(value) || this.optional(element);
}, "<span style='color:#FF0000'>&nbsp;&nbsp;请正确填写手机号码</span>");
</script>

<form action="do.php?ac=register" method="post" id="regforms"
    name="regforms">
<table>
    <tr>
        <td>用户名：</td>
        <td><input name="username" id="username" type="text"
            class="textmet" /></td>
    </tr>
    <tr>
        <td>手机号：</td>
        <td><input name="mobile" id="mobile" type="text"
            class="textmet" /></td>
    </tr>
    <tr>
        <td>邮箱：</td>
        <td><input name="email" id="email" type="text" class="textmet" /></td>
    </tr>
    <tr>
        <td>密码：</td>
        <td><input name="password" id="password" type="password"
            class="textmet" /></td>
    </tr>
    <tr>
        <td>确认密码：</td>
        <td><input name="confirm_password" id="confirm_password"
            type="password" class="textmet" /></td>
    </tr>
    <tr>
        <td>密码提示：</td>
        <td><input name="question" id="question" type="text"
            class="textmet" /></td>
    </tr>
    <tr>
        <td>密码答案：</td>
        <td><input name="answer" id="answer" type="text"
            class="textmet" /></td>
    </tr>
    <tr>
        <td>&nbsp;</td>
        <td><input name="registersubmit" id="registersubmit"
            type="submit" class="btnzhuce" value="注册" /> <input type="hidden"
            name="formhash" value="<{formhash()}>" /></td>
    </tr>
</table>

</form>

 

/do.php?ac=ajax  代码该怎么写？

我的伪代码如下：

 

  if($_POST['username']=="zhangsan"){
           echo "false";
     }

 

以上可以验证 但是有个问题是：

    以上html 代码中 js 部分修改成:

   date:{
            username:function(){return $("#username").val();   };
   }