Subtracting Time from a Time - Help

<?php
$channel = "mattbenson";
$json_file = @file_get_contents("http://api.justin.tv/api/stream/list.json?channel={$channel}", 0, null, null);
$json_array = json_decode($json_file, true);

if( array_key_exists( '0', $json_array )
&& array_key_exists( 'channel', $json_array[0] )
&& $json_array[0]['name'] == "live_user_{$channel}" )
{
$channelTitle = $json_array[0]['channel']['title'];
$title = $json_array[0]['channel']['status'];
$viewers = $json_array[0]['channel_count'];
$uptime = $json_array[0]['up_time'];
$today = date("D M j d:i:s Y");
$uptime1 = ($today - $uptime);

printf('Online');

printf ($uptime1);

print "<br>";
print "date <--- ";
printf ($today);
print "<br>";
print "uptime <--- ";
printf ($uptime);
}
else
{
printf('Offline');
}

?>


It displays like this
http://gyazo.com/fb3c95029c79da2a1a0855ee8a6aa353.png?1349530088

Problem is it doesn't subtract is just displays 0

Anyhelp?

You cannot subtract strings.
$today should be time(), and $uptime MUST be an integer. Then you can subtract and create $uptime1. That will give you the number of seconds $uptime is which you can format into whatever display.
If you have 5.3+, you can use the dateinterval.

$dtUptime = new DateTime($json_array[0]['up_time']); // this now assumes a string GNU valid format
$dtNow = new DateTime();
$diDiff = $dtNow->diff($dtUptime, true);
print $diDiff->format("Uptime: %a days");