how to access values in jquery muiltiselect through php

Question

I'm using jquery multiselect and in options i'm fetching data from database these are basically available seats in a buss.. when user selected some seats and press the button i'm putting values on $_POST and using update query updating selected seats as reserved please help here is the code

** HTML SELECT tag with jquery and php for fetching data this is working fine **

<form action="" method="post">
    <label for="required">Required</label>
    <select id="required" multiple="multiple" data-placeholder="Select attendees..." name="required">
     <?php 

$con =   mysql_connect("localhost","root","") or die(mysql_error());
$link =      mysql_select_db("bus") or die(mysql_error());

     $query = " select seats.seatNo from seats where seats.isactive = 0 and seats.busID = 1";
     $result = mysql_query($query);
     while($row = mysql_fetch_array($result))
     {
         $seatNo = $row['seatNo'];
         ?>

     <option> <?php echo $seatNo ?> </option>

     <?php } ?>

    </select>

And then I'm getting selected seats here and updating the db

<?php

$con;
$link;
if(isset($_POST['submit']))
{
for($i = 0; $i<5; $i++)
{
$selected = $_POST['required'];
}
$insert = " update seats set seats.isactive = 1 where seats.seatNo = $selected and      seats.busID = 1";
$q = mysql_query($insert) or die(mysql_error());

if($q)
{
echo " record updated ";    
}

else
{
echo " couldn't update ";   
}

} 



?>