Ajax submits mobile phone number to database for verification and returns status value example detailed explanation

<script type="text/javascript">
 $(function(){
 $(&#39;.agree_regi&#39;).click(function(){
  var phone = $.trim($("#phone").val());
  if(phone == ""){
  NewAlert(2,"请输入手机号",null);
  return false;
  }else{
   var reg = /^0?1[3|4|5|8|7][0-9]\d{8}$/;
   if (!reg.test(phone)) {
    NewAlert(2,"请输入有效的手机号码",null);
     return false;
    }
  }
  var data ={
  phone:phone,
  };
  
  $.ajax({
  type:"POST",
  url:"{:U(&#39;Register/PhoneFind&#39;)}",
  data:data,
  success:function(msg){
   if(msg==&#39;0&#39;){
   NewAlert(2,"手机号有误",null);
   }
   if(msg==&#39;1&#39;){
   NewAlert(2,"该手机号已经注册，请直接登录",null);
   }
   if(msg==&#39;2&#39;){
   location.href="/Register/Regowner?phone="+phone;
   }
   if(msg==&#39;3&#39;){
   location.href="/Register/Regnest?phone="+phone;
   } 
  }
  });
 });
 });
</script>

public function PhoneFind(){
  if(!empty(I('param.phone'))){ //I方法获取post提交的值
   $phone = I('param.phone');
   $user = M("cuser");
   $res=$user->where(array('phone' =>$phone))->find(); //去数据库查询一条，并以数组返回
   if (!empty($res['password'])) {
    $status=1;//密码存在，用户直接登录
   }elseif(!empty($res)){
    $status=2;//存在，没有密码，设置密码，是业主
   }else{
    $status=3;//不存在，是游客，注册
   }
  }else{
   $status=0;//手机号有误
  }
  $this->ajaxReturn($status);         //返回状态值给前台
 }