<?php
function to_unix($time) {
$expl = explode(' ', $time);
$year = explode('-',$expl[0]);
$time = explode(':', $expl[1]);
$unix = mktime($time[0],$time[1],$time[2],$year[1],$year[2],$year[0]);
return $unix;
}
$time = '2013-10-28 12:00:00';
echo to_unix($time);
?>