时间的处理方式

protected function _normalizeDateRange(&$startDate, &$endDate)
{
    if (empty($startDate) && empty($endDate)) {
        return;
    }

    if (empty($startDate) && !empty($endDate) ) {
        throw new \Exception("参数不正确", BaseException::ERROR_CODE_ILLEGAL_PARAMETER);
    }
    if (!empty($startDate) && empty($endDate)) {
        $endDate = $startDate;
    }

    $startTimestamp = strtotime($startDate);
    $endTimestamp = strtotime($endDate);

    if ($startTimestamp === false) {
        throw new \Exception("日期格式非法", BaseException::ERROR_CODE_ILLEGAL_PARAMETER);
    }
    if($endTimestamp === false){
        throw new \Exception("日期格式非法", BaseException::ERROR_CODE_ILLEGAL_PARAMETER);
    }

    if ($startTimestamp > $endTimestamp) {
        throw new \Exception("日期范围非法", BaseException::ERROR_CODE_ILLEGAL_PARAMETER);
    }

    $startDate = date('Y-m-d 00:00:00', $startTimestamp);
    $endDate = date('Y-m-d 23:59:59', $endTimestamp);
}
这是经典的修改引用赋值例子