Пишем в шапке сайта:

<?php

$count = mysql_result(mysql_query('SELECT COUNT(`id`) FROM `mail_mess` WHERE `to_id` = "'.$user['id'].'" AND `read` = "0"'),0);

?>



Новых сообщений: <span id="count_mess"><?=$count; ?></span><br />



<script type="text/javascript" src="javascript/refresh_count_mess.js"></script>



Файл javascript/refresh_count_mess.js

$(function() {

setInterval('refresh_count_mess()', 1500);

});



function refresh_count_mess() {

$.ajax({

url: "javascript/refresh_count_mess.php",

cache: false,

dataType: "json",

success: function(result) {

$('#count_mess').html(result.count);

}

});

}



Файл: javascript/refresh_count_mess.php

<?php

require_once 'engine/connect.php'; // Подключение к бд

require_once 'engine/core.php'; // Настройки пользователя и т.п.



if (isset($user)) $count = mysql_result(mysql_query('SELECT COUNT(`id`) FROM `mail_mess` WHERE `to_id` = "'.$user['id'].'" AND `read` = "0"'),0);

else $count = 0;



$result = array('count' => $count);

echo json_encode($result);

?>