AJAX - PHP event on listbox selection change

how can i get the query to run on any listbox selection change

if(isset($_POST['select'])){  
 $newselection=$_POST['select']; 
 $query  = "SELECT count(*) FROM listings where description=" . $newselection. "";
 $result = mysql_query($query);
 while($row = mysql_fetch_array($result, MYSQL_ASSOC))
 {
     echo "Number of rows: {$row['count(*)']}";
 }
}

currently it only works when submit button is pressed

i'm trying to avoid js..

* Also i have other queries running ajax

if(isset($_POST['button1'])){ 
$selection=$_POST['select']; 
$queryres  = "SELECT * FROM listings wh开发者_如何学JAVAere description=" . $selection. "";
$resultres = mysql_query($queryres);
while($rowres = mysql_fetch_array($resultres, MYSQL_ASSOC))
 {

    echo "<div style='position: absolute; left: 294px; top: 16px;' title='Site map' class='myclass'> <img src={$rowres['picture1']} alt=''/></div>" ;
    echo "<div style='position: absolute; left: 294px; top: 116px;' class='myclass'>Number:{$rowres['number']} <br>Description : {$rowres['description']} <br><br></div>" ;
 }
 }

try this (it has nothing to do with php code, it's html)

<option onchange="this.submit();">

JS is the only alternative to the user clicking the submit button. Something like <select onchange="submit();"> would probably suffice.