php取得年の開始時間と終了時間

    $startTime = $year.'-'.$smonth.'-1 00:00:00';
    $em = $year.'-'.$emonth.'-1 23:59:59';
    $endTime = date('Y-m-t H:i:s',strtotime($em));

    return array('stime'=>strtotime($startTime),'etime'=>strtotime($endTime));
}