$('button').on('click',function(){;
      var booluser = $('#data input')[0].value.length >= 8;
      var   boolpwd = $('#data input')[1].value.length >= 6 ;
      var boolpwd1 = $('#data input')[1].value == $('#data input')[2].value ;
      var retel =/^(13[0-9]|14[5|7]|15[0|1|2|3|5|6|7|8|9]|18[0|1|2|3|5|6|7|8|9])\d{8}$/g; 
      var booltel = retel.test($('#data input')[3].value);
      var reemail = /^\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$/g ;
      var boolemail = reemail.test($('#data input')[4].value);
      //这里应该嵌套使if的,但是不是实际开发,这么写便于代码观看
      if(!booluser){
        console.log('user:不能少于8位');
      }
      if(!boolpwd){
        console.log('pwd:不能少于6位');
      }
      if(!boolpwd1){
        console.log('pwd1:两次输入密码不一致');
      }
      if(!booltel){
        console.log('tel:请输入正确的电话号');
      }
      if(!boolemail){
        console.log('email:请输入正确的邮箱格式');
      }

if(booluser && boolpwd && boolpwd1 && booltel && boolemail){        
        $.ajax({
          type:"get",
         
          url:"reg.php",
          async:true,
          data:{

            user:$('#data input')[0].value,
            pwd:$('#data input')[1].value,
            tel:$('#data input')[3].value,
            email:$('#data input')[4].value
          },
          success : function(data){
            console.log(data);
          }
        });
      }
      })

<?php
var_dump($_GET);
$user = $_GET['user'];
$pwd = $_GET['pwd'];
$tel = $_GET['tel'];
$email = $_GET['email'];
$msg = '';
header('Content-type:text/html;charset=utf8');
  $adders = "mysql:host=localhost;dbname=Users;";
  $db = new PDO($adders,"root");
  $db->exec('set names utf8');
  //链接数据库,创建表
  $result = $db->exec('create table if not exists ajaxreg(user varchar(100) 
     primary key,pwd varchar(100),tel varchar(30),email varchar(30)) 
     default charset=utf8');
  $resulttel = $db->query("select tel from ajaxreg ");
  $resulttel->setFetchMode(PDO::FETCH_ASSOC);
  $arr = $resulttel->fetchAll();
 
  foreach($arr as $ar){
    if( $ar['tel'] == $tel){
      $msg = "您输入的手机号已经存在";
     echo $msg;
    //如果手机号已存在,终止整个程序
    die();
    }
  }
     //如果手机号不存在执行下面代码
     $result = $db->exec("insert into ajaxreg values(
     '$user','$pwd','$tel','$email')");
     if($result){
      $msg = "注册成功";
     }else{
     $msg = "用户名已存在";
     }
  echo $msg;
 $db->close();
?>