i have a drop down list populated with values from database. What i am trying to achieve is assign a select statement to each value.

Populate menu code
<?php
require 'conn.php';
$filter=mysql_query("select distinct fuel_type from car");
while($row = mysql_fetch_array($filter)) {
$options .="<option>" . $row['fuel_type'] . "</option>";
$menu="<form id='filter' name='filter' method='post' action=''>
<p><label>Filter</label></p>
<select name='filter' id='filter'>
" . $options . "
</select>
</form>";
}
echo $menu;
?>
Now this menu will be used to filter out car listing and will be placed on the sidebar

How can i assign each value from the drop down list a different select statement like;
select * from car where fuel_type = (dropdown list value selected) without having to submit the form.
perhaps something like the following?
if($_GET["filter"] == 'Petrol'){
$query=mysql_query("select * from car where fuel_type = 'Petrol'");
header("Location: cars.php");
}
$_GETor$_POST