将下拉列表转换为组合框php - sql

in below code i can fetch all my usernames. my problem is users are too many and finding too many users in drop down list is very very hard work so i need a combo box that i can write there and find people.

it is my code that uses a drop down list:

<?php   

$user_id =$fgmembersite->UserID();

   $db_host = 'localhost';
   $db_name= 'site';
   $db_table2= 'tablesite';
   $db_user = 'root';
   $db_pass = '';

$con2 = mysql_connect($db_host,$db_user,$db_pass) or die("خطا در اتصال به پايگاه داده");
$selected=mysql_select_db($db_name, $con2) or die("خطا در انتخاب پايگاه داده");
mysql_query("SET CHARACTER SET  utf8");

$dbresult=mysql_query("SELECT *
                       FROM  $db_table2 WHERE id_user != '$user_id'",$con2);
    echo'* نام کاربری که به او خدمت داده اید: ','<br/>';                       
echo '<select name="users" dir="rtl">';

while($amch=mysql_fetch_assoc($dbresult))
{ 
   echo '<option value="'.$amch['id_user'].'">'.$amch['username'].'</option>';
}
echo '</select>'; ?><br/>

a thing like this:

http://jqueryui.com/autocomplete/#combobox

You will need to use some Ajax for this, here is full example/tutorial about how to create your autocomplete http://www.pontikis.net/blog/jquery-ui-autocomplete-step-by-step