PHP timestamp date to user timezone

Question

I'm pulling the raw generated mysql timestamp info of $item_date from the database as php date format:

if (($timestamp = strtotime($item_date)) === false) {
    echo "The timestamp string is bogus";
} else {
    echo date('j M Y h:i:sA', $timestamp);
}

Output folowwing the server zone (UTC):

12 Nov 2012 05:54:11PM

but i want it to convert according to the user time zone

Example: let's say if the user's time is 13 Nov 2012 07:00:00 AM(+0800 GMT) and the server time is 12 Nov 2012 11:00:00 PM(UTC) and the timestamp of $item_date is 12 Nov 2012 10:30:00 PM (UTC) so

User with (UTC) will see $item_date as:

12 Nov 2012 10:30:00 PM

and user with (+0800 GMT) will see $item_date as:

13 Nov 2012 06:30:00 PM

How do i get it done? Thanks

Answer 1

This post has been updated to include a full-fledged example

<?php
    session_start();

    if (isset($_POST['timezone']))
    {
        $_SESSION['tz'] = $_POST['timezone'];
        exit;
    }

    if (isset($_SESSION['tz']))
    {
        //at this point, you have the users timezone in your session
        $item_date = 1371278212;

        $dt = new DateTime();
        $dt->setTimestamp($item_date);

        //just for the fun: what would it be in UTC?
        $dt->setTimezone(new DateTimeZone("UTC"));
        $would_be = $dt->format('Y-m-d H:i:sP');

        $dt->setTimezone(new DateTimeZone($_SESSION['tz']));
        $is = $dt->format('Y-m-d H:i:sP');

        echo "Timestamp " . $item_date . " is date " . $is . 
             " in users timezone " . $dt->getTimezone()->getName() .
             " and would be " . $would_be . " in UTC<br />";
    }
?>

<script type="text/javascript" src="http://code.jquery.com/jquery-latest.min.js"></script>
<script src="http://cdnjs.cloudflare.com/ajax/libs/jstimezonedetect/1.0.4/jstz.min.js"></script>
<script language="javascript">
  $(document).ready(function() {
        <?php if (!isset($_SESSION['tz'])) { ?>
            $.ajax({
                type: "POST",
                url: "tz.php",
                data: 'timezone=' + jstz.determine().name(),
                success: function(data){
                    location.reload();
                }
            });

        <?php } ?>        
    });
</script>

I hope this is now clear enough ;).