php ajax-仅在返回的数据不为空时自动刷新div

Question

I am using bootstrap , php and mysql for an application . With this , whenever the users are logged in , the admin will post messages across to all users that will be displayed as an alert on the page . Below is my ajax code :

$.ajaxSetup(
    {
        cache: false,
        beforeSend: function() {
            $('#admin_message').hide();
        },
        complete: function() {
            $('#admin_message').show();
        },
        success: function() {
            $('#admin_message').show();
        }
    });
    var $admin_msg = $("#admin_message");
    $admin_msg.load("get_message_board.php");        
    var refreshId = setInterval(function()
    {
        $admin_msg.load('get_message_board.php');
    }, 10000);

Below is my alert holder holder

    <div class="alert alert-success" id="alert_holder">
<p id="admin_message" style="text-align: center;font-size: 20px"></p>
</div>

PHP SCRIPT :

include './functions.php';

    $sql = "select message from msg_db3 where user_group ='".$_SESSION['active_user_group']."' order by id DESC LIMIT 1";
    $temp = return_results($sql);

    echo $temp['0']['message'];

Now i want to make sure that the div (with id='alert_holder') is hidden by default and shows up only if echo $temp['0']['message'] is not empty .If it is empty , it should be hidden . Also the transition is a bit odd since it shakes the entire page while bringing the alert up on the screen .

Please advice on the above .

THanks in advance .

Answer 1

EDIT: can you try with normal Ajax?

$.ajax({
  url: "get_message_board.php"
})
.done(function( data) {
console.log(data);
 if(data.length>0){
       $('#admin_message').show();
     } else {
       alert('not found');
     }
}
});

Check your response length and show if it's not null

success: function(data) {
 if(data.length>0){
   $('#admin_message').show();
 }
}

In php script you can change to

if(isset($temp['0'])){
 echo $temp['0']['message'];
}

Answer 2

The main problem with your code is with

complete: function() {
            $('#admin_message').show();
        },

This code will show #admin_message every time when ajax is completed. if you remove this unnecessary part you can make only my first change with if detection.