php响应变慢（用mysql）

I'm developing a dashboard, it've a notifications also so i planned for a live notifications with ajax,php,mysql.i've made it possible but the mysqli(from php) reads is slow for fetch results from database,below is my code

this is my javascript code on index.php:

comres = {
                            connect: function() {

                                    return $.ajax({
                                            url: 'read_notification.php',
                                            type: 'POST',

                                            success: function(evt, request) {
                                                     alert(evt);

                                            },
                                            complete: function() {

                                                    comres.connect();
                                            }
                                    });
                            }

                    }

                    $(document).ready(function() {

                            comres.connect();
                    });

below is my read_notification.php

<?php




 require_once("db.php");



 $query=mysqli_query($db,"select * from notifications");

while(mysqli_num_rows($query) < 1)
{
}

$query1 = mysqli_query($db,"select * from notifications");

 $row = mysqli_fetch_array($query1);

 $id=$row['id'];
  $notification=$row['notification'];



 echo "you have a notification ".$notification

mysqli_query($db,"delete from ticket.handover_response where id='$id'");


 ?>

below is working flow

1. javascript calls the read_notification.php when loads the index.php
2. read_notification.php fire the query to database with while loop,while loop continuous still the database have any one entry on notification table
3. when the database table have a entry the while loop get fails and the response back to the index.php

here no problem is in working flow but i've a delay on after have a record on database(php is not reading suddenly from database,it's working after few more seconds), please suggest the reason or solution for this, thanks

Try this

$(document).ready(function() {
setInterval(function(){
//set up an ajax request every 2 sec
   comres.connect();
},2000);
});

In your php simply display new notification based on some flag variable.that is if user click the notification set the flag to one (dont show again)otherwise mark it as zero.