PHP time conversion code for Unix timestamp

/**
Time Convert Unix Timestamp
link: http://bbs.it-home.org
*/
date_default_timezone_set('Asia/Chongqing');
$time1 = "2013-02-16 08:40:54";
$time2 = strtotime ($time1);
echo $time2;
echo date('Y-m-d h:i:s',$time2);
?>