在yii2中将UTC时间转换为PST？

I am saving date/time in UTC timezone in my database. like : 2015-07-22 17:08:11

I want to convert this time to pacific time zone 2015-07-22 11:07:18.

Yet know I am using this function :

public static function UTCToPST($format, $time) {
    $dst = intval(date("I", $time));
    $tzOffset = intval(date('Z', time()));
    return date($format, $time + $tzOffset - 28800 + $dst * 3600);
  }

What should I have to do to get time in 2015-07-22 11:07:18 format? or there is any other good way in yii2 for this ?

Thanks.

I always store date/time as Unix Time Stamp in database (use INT(11) in MySQL)

Because it is Unix Time Stamp, simply use PHP date() to convert it to datetime to your predefined timezone