日期字串格式和时间戳格式转化

function to_timespan($str, $format = 'Y-m-d H:i:s'){
$timezone = intval(C('TIME_ZONE'));
//$timezone = 8;
$time = intval(strtotime($str));
if($time!=0)
$time = $time - $timezone * 3600;
return $time;


}
function to_date($utc_time, $format = 'Y-m-d H:i:s') {
if (empty ( $utc_time )) {
return '';
}
$timezone = intval(C('TIME_ZONE'));
$time = $utc_time + $timezone * 3600;
return date ($format, $time );
}