/*
* 时区转换
*/
function toTimeZone($src, $from_tz = 'America/Denver', $to_tz = 'Asia/Shanghai', $fm = 'Y-m-d H:i:s') {
$datetime = new DateTime($src, new DateTimeZone($from_tz));
$datetime->setTimezone(new DateTimeZone($to_tz));
return $datetime->format($fm);
}